JP5041283B2 - Zoom lens, optical apparatus, and imaging method - Google Patents

Description

  The present invention relates to a zoom lens used in an optical apparatus such as a digital still camera.

  Optical devices such as digital still cameras and video cameras are generally equipped with zoom lenses, and many suitable zoom lenses have been proposed (see, for example, Patent Document 1). Nowadays, portability has become very important in optical devices such as digital still cameras, and the zoom lens, which is a photographic lens, has become smaller and lighter in order to make the camera body smaller, thinner and lighter. It is illustrated. Among them, a zoom lens has been devised that includes an optical element capable of bending an optical path about 90 degrees in a part of a lens system. By mounting such a zoom lens, it does not protrude from the camera body when shifting from the storage state to the use state, and is excellent in portability even in the use state. In addition, it greatly contributes to miniaturization and thinning of the camera.

By the way, many zoom lenses equipped with an optical element that can bend the optical path by about 90 degrees give priority to downsizing and thinning, so that the focal length at the wide-angle end state is large, and the wide angle of view is poor. It was. For this reason, the user cannot shoot a wider range or get closer to the subject to obtain a perspective effect. The conventional zoom lens capable of bending the optical path is configured to include a plurality of lens groups arranged in order from the object side, and the optical path is provided to the first lens group arranged closest to the object side among the plurality of lens groups. There is an optical path bending element that bends and a plurality of lens components arranged on the object side of the optical path bending element.
JP 2006-171492 A

  However, in such a conventional zoom lens, unless the lens component arranged closer to the object side than the optical path bending element is enlarged, the angle of view cannot be widened, and photographing at the wide-angle end is limited. There was a problem that.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a zoom lens, an optical apparatus, and an imaging method that can obtain a small and high imaging performance while having a wide angle of view. And

In order to achieve such an object, the zoom lens according to the present invention is a zoom lens including a plurality of lens groups arranged in order from the object side along the optical axis, and is the most object among the plurality of lens groups. The first lens group arranged on the side has a positive refractive power, and includes an optical path bending element that bends the optical path, and a plurality of lenses that are disposed on the object side of the optical path bending element. The plurality of lenses include at least one negative lens having a refractive index with respect to d-line exceeding 1.90, and a second lens group arranged on the image side of the first lens group among the plurality of lens groups has a negative refractive index. Where the focal length of the entire lens system in the wide-angle end state is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2.
1.9 <f1 / (− f2) <2.5
1.2 <(− f2) / fw <1.8
The conditions are satisfied.

In the above-described invention, when the refractive index for the d-line of the negative lens closest to the object among the plurality of lenses is nd1, the following formula nd1> 1.90.
When the refractive index for the d-line of the most negative lens on the image side among the plurality of lenses is nd2, the following formula nd2> 1.90 is satisfied.
It is preferable to satisfy the following conditions.

In the above-described invention, it is preferable that the plurality of lenses be two lenses.

In the above method, the refractive index for the negative lens at the d-line closest to the object side among the plurality of lenses and nd1, the refractive index at the d-line of the negative lens on the most image side among the plurality of lenses and nd2 Then, the following formula 0.7 <nd1 / nd2 <1.1
It is preferable to satisfy the following conditions.

In the above invention, when the Abbe number of the negative lens closest to the object side among the plurality of lenses is νd1, the following equation νd1 <50
When the Abbe number for the d-line of the negative lens closest to the image among the plurality of lenses is νd2, the following equation is satisfied: νd2 <50
It is preferable to satisfy the following conditions.

In the above method, the plurality of the Abbe number at the d-line of the negative lens on the most object side of the lens is vd1, and νd2 the Abbe number at the d-line of the negative lens on the most image side among the plurality of lenses Then, the following formula 0.4 <νd1 / νd2 <1.3
It is preferable to satisfy the following conditions.

In the above-described invention, the optical path bending element is a prism, and a distance on the optical axis from the most object-side surface to the prism in the first lens group is L1, and a distance on the optical axis of the prism is When Lp is satisfied, the following formula L1 / Lp <1.0
It is preferable to satisfy the following conditions.

In the above-described invention, the optical path bending element is a prism, and when the refractive index of the prism with respect to the d-line is ndp, the following formula ndp> 1.80
It is preferable to satisfy the following conditions.

  In the above invention, the plurality of lens groups are arranged in order from the object side along the optical axis, the first lens group, the second lens group, the third lens group, and the fourth lens group. It is preferable that it is comprised.

  In the above-described invention, the second lens group has a negative refractive power, the third lens group has a positive refractive power, and the fourth lens group has a positive refractive power. It is preferable.

  In the above invention, the first lens group and the third lens group are fixed during zooming from the wide-angle end to the telephoto end, and the second lens group and the fourth lens group are the wide-angle end. It is preferable to move along the optical axis during zooming from the telephoto end to the telephoto end.

In the above-described invention, it is preferable that the plurality of lenses include a negative meniscus lens having a convex surface facing the object side.

  In the above-described invention, it is preferable that the first lens group includes a positive lens disposed on the image side of the optical path bending element.

In the above-described invention, it is preferable that the first lens group includes an aspheric lens .

  In the above-described invention, it is preferable that the angle of view in the wide-angle end state is 75 degrees or more.

  The optical apparatus according to the present invention is an optical apparatus including a zoom lens that forms an image of an object on a predetermined surface, wherein the zoom lens is the zoom lens according to the present invention.

The imaging method according to the present invention is an imaging method in which an image of the object is formed on a predetermined plane using a zoom lens having a plurality of lens groups arranged in order from the object side along the optical axis. The first lens group arranged closest to the object side among the plurality of lens groups has a positive refractive power, the first lens group is provided with an optical path bending element for bending an optical path, and the optical path bending is performed. arranging a plurality of lenses on the object side of the element, the multiple lenses, at least not one containing a negative lens having a refractive index greater than 1.90 at the d-line, the first lens of the plurality of lens groups The second lens group arranged on the image side of the group has a negative refractive index, the focal length of the entire lens system in the wide-angle end state is fw, the focal length of the first lens group is f1, and the second lens If the focal length of the group is f2, , The following equation
1.9 <f1 / (− f2) <2.5
1.2 <(− f2) / fw <1.8
To meet the requirements of

  According to the present invention, it is possible to obtain a small and high imaging performance while having a wide angle of view.

  Hereinafter, preferred embodiments of the present application will be described with reference to the drawings. A digital still camera CAM equipped with a zoom lens ZL according to the present application is shown in FIG. 1A is a front view of the digital still camera, and FIG. 1B is a rear view thereof. FIG. 2 is a cross-sectional view taken along arrow II-II in FIG. 1A and shows an outline of a zoom lens ZL described later.

  In the digital still camera CAM shown in FIGS. 1 and 2, when a power button (not shown) is pressed, a shutter (not shown) of the photographing lens (ZL) is opened, and light from the subject (object) is captured by the photographing lens (ZL). Are condensed and imaged on the image sensor C arranged on the image plane I. The subject image formed on the image sensor C is displayed on the liquid crystal monitor M disposed behind the digital still camera CAM. The photographer determines the composition of the subject image while looking at the liquid crystal monitor M, and then depresses the release button B1 to photograph the subject image with the image sensor C, and records and saves it in a memory (not shown).

  The photographic lens is composed of the zoom lens ZL according to the present application, and light incident from the front of the digital still camera CAM is moved approximately 90 degrees downward (downward in the drawing in FIG. 2) by the optical path bending element P in the zoom lens ZL. Since the optical path is bent, the digital still camera CAM can be thinned. Further, the digital still camera CAM has an auxiliary light emitting unit D that emits auxiliary light when the subject is dark, and a wide (W) when zooming the zoom lens ZL from the wide-angle end state (W) to the telephoto end state (T). ) -Tele (T) button B2 and function button B3 used for setting various conditions of the digital still camera CAM.

  The zoom lens ZL includes, in order from the object side along the optical axis, a first lens group G1 having an optical path bending element P and having a positive refractive power, a second lens group G2 having a negative refractive power, The lens unit includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power. In zooming from the wide-angle end to the telephoto end, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane I, and the second lens group G2 and the fourth lens group G4 are along the optical axis. The distance between the first lens group G1 and the second lens group G2 is increased, the distance between the second lens group G2 and the third lens group G3 is decreased, and the third lens group G3 and the fourth lens group G4 are moved. The distance from the lens group G4 is reduced. A filter group LP including a low-pass filter and an infrared cut filter is disposed between the zoom lens ZL and the image plane I.

  The first lens group G1 has an action of bending the optical path by approximately 90 degrees and an action of converging the light flux. Further, the first lens group G1 is always fixed during zooming from the wide-angle end to the telephoto end. As described above, the first lens group G1, which is the largest lens group in the zoom lens ZL and has a large weight, is not moved, so that the structure can be simplified.

  The second lens group G2 has a function of enlarging an image of a subject (object) formed by the first lens group G1, and the first lens group G1 and the second lens group move from the wide-angle end state to the telephoto end state. The focal length is changed by increasing the enlargement ratio by increasing the distance from G2.

  The third lens group G3 has a function of converging the light beam expanded by the second lens group G2, and in order to achieve high performance, the third lens group G3 is composed of a plurality of lens components, and spherical aberration and Sign condition and Petzval sum are well corrected.

  The fourth lens group G4 has a function of further converging the light beam converged by the third lens group G3, and the third lens group is used when changing the focal length from the wide-angle end state to the telephoto end state (during zooming). By actively changing the distance between G3 and the fourth lens group G4, it is possible to suppress fluctuations in the image plane with respect to changes in focal length.

  In the zoom lens ZL having such a plurality of lens groups, the first lens group G1 arranged closest to the object side among the plurality of lens groups has a positive refractive power and an optical path bending element P that bends the optical path, and The plurality of lens components are arranged on the object side of the optical path bending element P, and the plurality of lens components includes at least one negative lens having a refractive index with respect to d-line exceeding 1.90. It is preferable that As a result, the refractive index of the lens component disposed on the object side relative to the optical path bending element P is increased, and therefore the angle of view at the wide-angle end is widened without increasing the effective diameter and outer diameter of the lens component. Is possible.

  If the refractive index is higher than 1.90, the curvature radius of the lens component can be increased and the curvature thereof can be moderated. Therefore, the interval on the optical axis of the plurality of lens components can be reduced to reduce the first lens. It becomes possible to reduce the size of the group G1, and further the entire zoom lens ZL. Furthermore, by arranging a plurality of lens components closer to the object side than the optical path bending element P, it is possible to satisfactorily correct spherical aberration and coma generated by the first lens group G1 alone. In this way, it is possible to obtain a zoom lens ZL that has a small angle and high imaging performance while having a wide field angle, and an optical device (digital still camera CAM) including the zoom lens ZL.

  At this time, when the refractive index with respect to the d-line of the negative lens closest to the object among the plurality of lens components is nd1, and the refractive index with respect to the d-line of the negative lens closest to the image is nd2, the following conditional expression (1 ) And the condition represented by the conditional expression (2) are preferably satisfied.

nd1> 1.90 (1)
nd2> 1.90 (2)

  Conditional expression (1) and conditional expression (2) are appropriate for the negative lens closest to the object side and the negative lens closest to the image side, which are disposed closer to the object side than the optical path bending element P in the first lens group G1. It is a conditional expression which prescribes | regulates a refractive index range. When the conditions of the conditional expressions (1) and (2) are not satisfied, the lens on the object side becomes larger than the optical path bending element P. That is, the effective diameter and the outer diameter of the negative lens in the first lens group G1 are increased, and the length from the optical path bending element P to the lens surface closest to the object side is increased. As a result, the thickness of the camera body is increased, which is not preferable. In addition, correction of coma aberration becomes difficult, and high optical performance cannot be obtained.

  In order to secure the effect of the present application, it is more preferable to set the lower limit value of conditional expression (1) and conditional expression (2) to 1.91. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit values of conditional expression (1) and conditional expression (2) to 1.92.

  The plurality of lens components are preferably two lenses. In this way, the first lens group G1 can be configured with a minimum number of components.

  Further, when the refractive index for the d-line of the negative lens closest to the object among the plurality of lens components is nd1, and the refractive index for the d-line of the negative lens closest to the image is nd2, the following conditional expression (3) is satisfied. It is preferable that the conditions expressed are satisfied.

  0.7 <nd1 / nd2 <1.1 (3)

  Conditional expression (3) defines a combination of optical material characteristics of a negative lens closest to the object side and a negative lens closest to the image side, which is disposed on the object side of the optical path bending element P in the first lens group G1. Conditional expression. When the condition exceeds the upper limit value of the conditional expression (3), the effective diameter and the outer diameter of the negative lens in the first lens group G1 are increased, which is not preferable. In addition, correction of coma aberration becomes difficult, and high optical performance cannot be obtained. On the other hand, when the condition is less than the lower limit value of the conditional expression (3), the lens on the object side with respect to the optical path bending element P is enlarged, and as a result, the thickness of the camera body is also affected. Further, the lateral chromatic aberration generated in the first lens group G1 is deteriorated, which is not preferable.

  In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (3) to 1.07. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (3) to 1.05. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (3) to 0.8. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit of conditional expression (3) to 0.9. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit of conditional expression (3) to 0.95.

  Further, when the Abbe number with respect to the d-line of the negative lens closest to the object among the plurality of lens components is νd1, and the Abbe number with respect to the d-line of the negative lens closest to the image is νd2, the following conditional expression (4) and It is preferable that the condition represented by conditional expression (5) is satisfied.

νd1 <50 (4)
νd2 <50 (5)

  Conditional expression (4) and conditional expression (5) are appropriate for the negative lens closest to the object side and the negative lens closest to the image side, which are disposed on the object side of the optical path bending element P in the first lens group G1. It is a conditional expression which prescribes | regulates the range of an optical material. If the conditions of conditional expression (4) and conditional expression (5) are not satisfied, it is difficult to correct axial chromatic aberration and lateral chromatic aberration that occur in the first lens group G1 alone. High optical performance cannot be obtained.

  In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) and conditional expression (5) to 37.0. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) and conditional expression (5) to 34.0. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) and conditional expression (5) to 32.0. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (4) and conditional expression (5) to 30.0.

  Further, when the Abbe number with respect to the d-line of the negative lens closest to the object among the plurality of lens components is νd1, and the Abbe number with respect to the d-line of the negative lens closest to the image is νd2, the following conditional expression (6) is satisfied. It is preferable that the conditions expressed are satisfied.

  0.4 <νd1 / νd2 <1.3 (6)

  Conditional expression (6) defines a combination of the optical material characteristics of the negative lens closest to the object side and the negative lens closest to the image side, which is disposed closer to the object side than the optical path bending element P in the first lens group G1. Conditional expression. When the condition exceeds the upper limit value of conditional expression (6), the effective diameter and the outer diameter of the negative lens in the first lens group G1 are increased, which is not preferable because the camera body is increased. In addition, correction of coma aberration becomes difficult, and high optical performance cannot be obtained. On the other hand, when the condition is lower than the lower limit value of the conditional expression (6), the lens on the object side becomes larger than the optical path bending element P, and as a result, the thickness of the camera body is also affected. Further, the lateral chromatic aberration generated in the first lens group G1 is deteriorated, which is not preferable.

  In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (6) to 1.07. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (6) to 1.05. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (6) to 0.93. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit of conditional expression (6) to 0.95.

  The optical path bending element P is a prism. When the distance on the optical axis from the most object side surface to the prism in the first lens group G1 is L1, and the distance on the optical axis of the prism is Lp, It is preferable that the condition represented by conditional expression (7) is satisfied.

  L1 / Lp <1.0 (7)

  Conditional expression (7) is an appropriate range between the distance on the optical axis from the most object side surface in the first lens group G1 to the optical path bending element P (prism) and the distance on the optical axis of the optical path bending element P. Is a conditional expression that prescribes When the condition exceeds the upper limit value of the conditional expression (7), the total length of the lens on the object side with respect to the optical path bending element P becomes longer, and the thickness of the optical system becomes thicker. As a result, the thickness of the camera body is also affected, making it impossible to reduce the size and thickness.

  In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (7) to 0.95. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (7) to 0.9.

  Further, when the focal length of the first lens group G1 is f1, and the focal length of the second lens group G2 arranged on the image side of the first lens group G1 among the plurality of lens groups is f2, the following conditional expression (8 It is preferable that the conditions represented by

  1.9 <f1 / (− f2) <2.5 (8)

  Conditional expression (8) is a conditional expression for defining an appropriate range for the focal length ratio of the first lens group G1 and the second lens group G2. When the condition exceeds the upper limit value of the conditional expression (8), the refractive power of the first lens group G1 becomes relatively weak, and the lens outer diameter of the entire first lens group G1 becomes large, thereby reducing the size. You will not be able to contribute. Further, since the refractive power of the second lens group G2 becomes relatively strong, the occurrence of coma aberration cannot be suppressed, and high optical performance cannot be obtained. On the other hand, when the condition is lower than the lower limit value of the conditional expression (8), the refractive power of the first lens group G1 becomes relatively strong, which is advantageous for downsizing. This is not preferable because the variation in curvature of field becomes large. In addition, since the refractive power of the second lens group G2 becomes relatively weak, the second lens group G2 cannot efficiently contribute to zooming, and the amount of movement necessary for zooming cannot be secured. End up.

  In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (8) to 2.45. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (8) to 2.4. In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (8) to 1.92. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit of conditional expression (8) to 1.95.

  As described above, the second lens group G2 arranged on the image side of the first lens group G1 among the plurality of lens groups has a negative refractive index, and the focal length of the entire lens system in the wide-angle end state. Is set to fw, and the focal length of the second lens group G2 is set to f2, it is preferable that the condition expressed by the following conditional expression (9) is satisfied.

  1.2 <(− f2) / fw <1.8 (9)

  Conditional expression (9) is a conditional expression for defining an appropriate focal length range of the second lens group G2. When the condition exceeds the upper limit value of the conditional expression (9), the refractive power of the second lens group G2 becomes strong, and coma and astigmatism generated by the second lens group G2 alone become too large, so that close-up shooting is performed. The performance change at the time becomes large, which is not preferable. As a result, it becomes difficult to shorten the shortest shooting distance. On the other hand, when the condition is lower than the lower limit value of the conditional expression (9), the refractive power of the second lens group G2 is weakened, and the amount of movement at the time of focus adjustment is increased, so that a drive system member necessary for movement is required. Etc. may increase in size and interfere with other members. Further, it is not preferable to reduce the size because the spherical aberration is deteriorated. As a result, it becomes impossible to save space when storing in the camera body.

  In order to secure the effect of the present application, it is more preferable to set the upper limit of conditional expression (9) to 1.75. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the upper limit of conditional expression (9) to 1.72. In order to secure the effect of the present application, it is more preferable to set the lower limit value of conditional expression (9) to 1.22. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit of conditional expression (9) to 1.23.

  The optical path bending element P is a prism, and it is preferable that the condition represented by the following conditional expression (10) is satisfied when the refractive index with respect to the d-line of the prism is ndp.

  ndp> 1.80 (10)

  Conditional expression (10) is a conditional expression that defines an appropriate refractive index range of a prism (for example, a right-angle prism) that is the optical path bending element P. The right-angle prism can deflect the optical path by total reflection, reduce light loss, and make the optical system compact. If the condition is less than the lower limit value of conditional expression (10), the prism shape becomes large, and the entire zoom lens becomes undesirably large. In addition, coma and lateral chromatic aberration generated in the first lens group G1 are deteriorated. As a result, the thickness of the camera body is also affected, making it impossible to reduce the size. In addition to the prism, a mirror, an optical fiber, or the like can be used for the optical path bending element P.

  In order to secure the effect of the present application, it is more preferable to set the lower limit of conditional expression (10) to 1.81. Furthermore, in order to ensure the effect of the present application, it is more preferable to set the lower limit of conditional expression (10) to 1.82.

  Further, as described above, the first lens group G1, the second lens group G2, and the third lens group G3 in which the plurality of lens groups constituting the zoom lens ZL are arranged in order from the object side along the optical axis. And the fourth lens group G4. In this way, the zoom lens ZL can be appropriately downsized.

  At this time, it is preferable that the second lens group G2 has a negative refractive power, the third lens group G3 has a positive refractive power, and the fourth lens group G4 has a positive refractive power. . In this way, desired optical performance can be obtained with a minimum configuration.

  At this time, the first lens group G1 and the third lens group G3 are fixed during zooming from the wide-angle end to the telephoto end, and the second lens group G2 and the fourth lens group G4 are moved from the wide-angle end to the telephoto end. It is preferable to move along the optical axis during zooming. In this way, fluctuations in aberration due to zooming can be reduced.

  Further, it is preferable that the plurality of lens components include a negative meniscus lens having a convex surface facing the object side. In this way, each lens component can be appropriately downsized.

  At this time, it is preferable that the first lens group G1 has a positive lens disposed on the image side of the optical path bending element P. In this way, desired optical performance can be obtained by combining with other lenses (for example, negative meniscus lenses).

  In addition, it is preferable that the first lens group G1 includes an aspheric lens component. In this way, it is possible to satisfactorily correct coma and astigmatism fluctuations that occur when the focal length changes (zooming) from the wide-angle end state to the telephoto end state. Furthermore, it is possible to contribute to downsizing of the lens outer diameter of the first lens group G1.

  In addition, the angle of view in the wide-angle end state is preferably 75 degrees or more, and more preferably 80 degrees or more. In this way, the angle of view can be widened, and the degree of freedom in shooting can be improved.

  In the present embodiment, in order to balance further higher performance and downsizing, the second lens group G2 is arranged in order from the object side along the optical axis, and a negative lens having a concave surface facing the image side, It is preferable that the lens is composed of a negative lens having a concave surface facing the object side and a cemented lens having a negative refractive power obtained by bonding a positive lens. In this way, coma and lateral chromatic aberration generated by the second lens group G2 alone can be favorably corrected with a simple configuration.

  Furthermore, it is preferable that the second lens group G2 has an aspheric lens component. By so doing, it is possible to satisfactorily correct coma variation that occurs when the focal length changes (zooming) from the wide-angle end state to the telephoto end state.

  Further, in the present embodiment, the third lens group G3 corrects spherical aberration generated by the third lens group G3 alone and makes the exit pupil position as far as possible from the image plane. It is preferable that the lens is composed of a lens and a cemented lens having a negative refractive power. Specifically, the positive lens is arranged in order from the object side along the optical axis and has a convex surface facing the object side, and the object side. It is preferable to include a cemented lens having a negative refractive power, in which a positive lens having a convex surface and a negative lens having a concave surface facing the image side are bonded together. In this way, the lens diameter can be reduced by converging the off-axis light beam and keeping it away from the optical axis by the positive lens having the convex surface facing the object side.

  Furthermore, it is preferable that the third lens group G3 includes an aspheric lens component. In this way, it is possible to satisfactorily correct spherical aberration and coma aberration fluctuations that occur when the focal length changes (zooming) from the wide-angle end state to the telephoto end state.

  Further, in the present embodiment, the fourth lens group G4 corrects spherical aberration generated by the fourth lens group G4 alone and makes the exit pupil position as far as possible from the image plane. It is preferable that the lens is composed of a lens and a cemented lens having a negative refractive power. Specifically, the positive lens is arranged in order from the object side along the optical axis and has a convex surface facing the object side, and the object side. It is preferable to include a cemented lens having a negative refractive power, in which a positive lens having a convex surface and a negative lens having a concave surface facing the image side are bonded together. In this way, the lens diameter can be reduced by converging the off-axis light beam and keeping it away from the optical axis by the positive lens having the convex surface facing the object side. Further, since the fourth lens group G4 as a whole has a positive refractive power, it is possible to move the exit pupil position away from the image plane, which is suitable for an optical system using a solid-state imaging element as a light receiving element.

  Furthermore, it is preferable that the fourth lens group G4 includes an aspheric lens component. In this way, it is possible to satisfactorily correct the field curvature variation that occurs when the focal length changes (zooming) from the wide-angle end state to the telephoto end state.

  Further, in the present embodiment, in order to prevent a shooting failure due to image blur caused by camera shake or the like that is likely to occur in a high zoom lens, a lens detection system and a drive unit that detect a blur in the lens system are used. In combination, the whole or a part of any one of the lens groups constituting the lens system may be decentered as a shift lens group. Image blur is corrected by driving the shift lens group by the drive means and shifting the image so as to correct image blur (fluctuation in image plane position) caused by the blur of the lens system detected by the blur detection system. Is possible. As described above, the zoom lens ZL of the present embodiment can function as a so-called anti-vibration optical system.

  Embodiments of the present application will be described below with reference to the accompanying drawings. As described above, the zoom lens ZL according to each embodiment includes the first lens group G1 having a positive refractive power and the second lens group having a negative refractive power, which are arranged in order from the object side along the optical axis. G2 includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power. Further, between the fourth lens group G4 and the image plane I, a filter group FL composed of a low-pass filter, an infrared cut filter, or the like is disposed.

  Also, as shown in FIG. 3, during zooming from the wide-angle end to the telephoto end, the second lens group G2 and the fourth lens group G4 move along the optical axis, and the first lens group G1 and the third lens group G3 is fixed with respect to the image plane I. At this time, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens group G4. The interval between and decreases. FIG. 3 shows the distribution of the refractive power of the zoom lens according to each embodiment of the present application and the movement of each lens group in the change in the focal length state (zooming) from the wide-angle end state (W) to the telephoto end state (T). FIG.

  Tables 1 to 5 are shown below, and these are the tables listing the values of the specifications in the first to fifth examples. In each table, f is the focal length, and F.I. NO represents the F number, 2ω represents the angle of view, and Bf represents the back focus. Further, the surface number indicates the order of the lens surfaces from the object side along the direction in which the light beam travels, and the refractive index and the Abbe number indicate values for the d-line (λ = 587.6 nm). Here, “mm” is generally used for the focal length f, the radius of curvature, the surface interval, and other length units listed in all the following specifications, but the optical system is proportionally enlarged or reduced. However, since the same optical performance can be obtained, it is not limited to this. The curvature radius “0.0000” indicates a plane, and the description of “1.00000”, which is the refractive index of air, is omitted.

  In each table, an aspheric surface marked with an asterisk (y) has a height in the direction perpendicular to the optical axis as y, and the optical axis from the tangential plane of each aspheric surface at the height y to each aspheric surface. The distance along the line (sag amount) is S (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic constant is Κ, and the aspheric coefficient of the nth order (n = 4, 6, 8, 10) is When Cn, it is expressed by the following conditional expression (11). In each embodiment, the secondary aspheric coefficient C2 is 0, and is not shown.

S (y) = (y ² / r) / {1+ (1−Κ × y ² / r ² ) ^1/2 }
^{+ C4 × y 4 + C6 ×} y 6 + C8 × y 8 + C10 × y 10 ... (11)

  In each table, the axial air space between the first lens group G1 and the second lens group G2 is d8, the axial air space between the second lens group G2 and the third lens group G3 is d13, The axial air space between the lens group G3 and the fourth lens group G4 is d19, and the axial air space between the fourth lens group G4 and the filter group FL is d24. These axial air intervals (d8, d13, d19, d24) change during zooming.

(First embodiment)
Hereinafter, the first embodiment of the present application will be described with reference to FIGS. 4 to 7 and Table 1. FIG. FIG. 4 is a diagram illustrating a configuration of the zoom lens according to the first example. In the zoom lens ZL of FIG. 4, the first lens group G1 is arranged in order from the object side, a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, and an optical path. It comprises an optical path bending element P such as a right-angle prism intended to be bent about 90 degrees, and a biconvex positive lens L13 having an aspheric surface on the object side. The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having an aspheric surface on the image side and a convex surface facing the object side, a biconcave negative lens, and a biconvex positive lens. It comprises a bonded negative cemented lens L22.

  The third lens group G3 is composed of a biconvex positive lens L31 having an aspheric surface on the object side, and a negative lens obtained by bonding a biconvex positive lens and a biconcave negative lens, which are arranged in order from the object side. And a cemented lens L32. The fourth lens group G4 is composed of a biconvex positive lens L41 having an aspheric surface on the image side, a positive meniscus lens having a convex surface on the object side, and a negative surface with a concave surface on the image side. It comprises a negative cemented lens L42 bonded with a meniscus lens. The filter group FL is disposed between the fourth lens group G4 and the image plane I.

  The image plane I is formed on an image pickup device (not shown), and the image pickup device is composed of a CCD, a CMOS, or the like (the same applies to the following embodiments). The aperture stop S is disposed in the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end to the telephoto end. In FIG. 4, the optical path bending element P is shown in a developed state.

  Table 1 below shows specifications in the first embodiment. The surface numbers 1 to 28 in Table 1 correspond to the surfaces 1 to 28 in FIG. In the first embodiment, the lens surfaces of the seventh surface, the tenth surface, the fourteenth surface, and the twenty-first surface are aspherical.

(Table 1)
[Overall specifications]
Wide angle end Medium focal length Telephoto end f = 4.76 to 10.90 to 13.60
F. NO = 3.39 to 4.50 to 5.10
2ω = 80.10 to 37.24 to 30.08
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number 1 18.5837 0.80 1.94594 17.98
2 9.2523 1.95
3 21.1675 0.80 1.94594 17.98
4 12.1051 1.95
5 0.0000 10.00 1.88300 40.76
6 0.0000 0.30
7 * 16.6856 2.59 1.77377 47.17
8 -17.4860 (d8)
9 120.1506 0.80 1.85135 40.10
10 * 8.6224 1.45
11 -11.4881 0.80 1.81600 46.62
12 8.5611 1.31 1.94594 17.98
13 -462.6937 (d13)
14 * 6.2540 1.52 1.58913 61.25
15 -23.4186 0.50
16 0.0000 0.50 (Aperture stop S)
17 16.9167 1.87 1.65160 58.55
18 -3.8752 0.80 1.83481 42.71
19 9.4841 (d19)
20 11.5818 2.15 1.60602 57.44
21 * −10.2025 0.20
22 5.6247 2.05 1.49700 81.54
23 36.4651 0.80 1.92286 20.88
24 5.3918 (d24)
25 0.0000 0.55 1.54437 70.51
26 0.0000 0.40
27 0.0000 0.50 1.51633 64.14
28 0.0000 (Bf)
[Aspherical data]
Surface number Κ C4 C6 C8 C10
7 -4.2112 + 6.3347 × 10 ^-5 -1.3742 × 10 ^-6 + 2.0994 × 10 ^-8 -2.1938 × 10 ^-10
10 -9.0000 + 1.8903 × 10 ^-3 -7.0975 × 10 ^-5 + 2.6340 × 10 ^-6 + 3.3830 × 10 ^-8
14 +0.2972 + 1.1297 × 10 ^-4 + 1.9446 × 10 ^-5 + 6.7916 × 10 ^-7 -1.0642 × 10 ^-8
21 +2.5363 + 6.8503 × 10 ^-4 -7.8123 × 10 ^-7 + 1.0665 × 10 ^-6 -4.1646 × 10 ^-8
[Variable interval]
Wide angle end Intermediate focal length Telephoto end f 4.7600 10.8950 13.6000
d8 1.2108 5.8514 6.6474
d13 6.4865 1.8460 1.0500
d19 5.9585 2.3201 1.1000
d24 5.1473 8.7857 10.0058
Bf 0.5999 0.5997 0.5996
[Conditional value]
nd1 = 1.94594
nd2 = 1.94594
νd1 = 17.98
νd2 = 17.98
L1 = 5.500
Lp = 10.000
fw = 4.76000
f1 = 14.008549
f2 = −6.63946
ndp = 1.88300
Conditional expression (1) nd1 = 1.94594
Conditional expression (2) nd2 = 1.94594
Conditional expression (3) nd1 / nd2 = 1.000
Conditional expression (4) νd1 = 17.98
Conditional expression (5) νd2 = 17.98
Conditional expression (6) νd1 / νd2 = 1.000
Conditional expression (7) L1 / Lp = 0.550
Conditional expression (8) f1 / (− f2) = 2.122
Conditional expression (9) (-f2) /fw=1.395
Conditional expression (10) ndp = 1.88300

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied. Further, L1 = 5.500 with respect to Lp = 10.000, and it can be seen that L1 can be made smaller than the conventional one.

  5 to 7 are graphs showing various aberrations of the first example with respect to the d-line (λ = 587.6 nm). That is, FIG. 5 is a diagram of various aberrations in the infinite focus state in the wide-angle end state (f = 4.76 mm), and FIG. 6 is the infinite focus state in the intermediate focal length state (f = 10.90 mm). FIG. 7 is a diagram of various aberrations in the infinitely focused state in the telephoto end state (f = 13.60 mm).

  In each aberration diagram, FNO represents an F number, and A represents a half angle of view with respect to each image height. In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. Further, in the aberration diagrams showing the spherical aberration, the solid line shows the spherical aberration, and the broken line shows the sine condition (sine condition). The description of the aberration diagrams is the same in the other examples. As is apparent from the respective aberration diagrams, in the first example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Second embodiment)
Hereinafter, the second embodiment of the present application will be described with reference to FIGS. FIG. 8 is a diagram illustrating a configuration of a zoom lens according to the second example. The zoom lens of the second example has the same configuration as the zoom lens of the first example except for the configuration of the second lens group, and the same reference numerals as those in the first example are given to the respective parts. Detailed description is omitted. The second lens group G2 of the second embodiment includes a biconcave negative lens L21 having an aspheric surface on the image side, a biconcave negative lens, and a convex surface on the object side, which are arranged in order from the object side. And a negative cemented lens L22 that is bonded to a positive meniscus lens.

  Table 2 below shows specifications in the second embodiment. The surface numbers 1 to 28 in Table 2 correspond to the surfaces 1 to 28 in FIG. In the second embodiment, the lens surfaces of the seventh surface, the tenth surface, the fourteenth surface, and the twenty-first surface are aspherical.

(Table 2)
[Overall specifications]
Wide-angle end Intermediate focal length Telephoto end f = 4.76 to 10.90 to 16.83
F. NO = 3.43 to 4.38 to 5.32
2ω = 80.12 to 37.24 to 24.50
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number 1 18.7424 0.80 1.94594 17.98
2 9.3864 1.95
3 21.6083 0.80 1.94594 17.98
4 12.2621 1.95
5 0.0000 10.00 1.88300 40.76
6 0.0000 0.30
7 * 16.8349 2.60 1.77377 47.17
8 −17.3291 (d8)
9 -30.3831 0.80 1.85135 40.10
10 * 9.5012 1.00
11 −33.3537 0.80 1.81600 46.62
12 7.2272 1.38 1.94594 17.98
13 51.7364 (d13)
14 * 6.1623 1.46 1.58913 61.25
15 -32.7052 0.50
16 0.0000 0.50 (Aperture stop S)
17 16.2574 1.85 1.65160 58.55
18 -3.7749 0.80 1.83481 42.71
19 9.8126 (d19)
20 11.0508 2.15 1.60602 57.44
21 * −11.7394 0.20
22 6.0262 2.05 1.49700 81.54
23 24.0461 0.80 1.92286 20.88
24 5.4797 (d24)
25 0.0000 0.55 1.54437 70.51
26 0.0000 0.40
27 0.0000 0.50 1.51633 64.14
28 0.0000 (Bf)
[Aspherical data]
Surface number Κ C4 C6 C8 C10
7 -3.8785 + 4.8309 × 10 ^-5 -8.3247 × 10 ^-7 +1.7 150 × 10 ^-9 + 4.4539 × 10 ^-11
10 -9.0000 + 1.3364 × 10 ^-3 -5.0474 × 10 ^-5 + 1.5973 × 10 ^-6 + 1.2041 × 10 ^-8
14 +0.4450 + 1.9519 × 10 ^-4 + 1.4324 × 10 ^-5 + 1.3179 × 10 ^-6 -6.5285 × 10 ^-9
21 +0.2452 + 3.9638 × 10 ^-4 + 1.2430 × 10 ^-7 + 4.3306 × 10 ^-7 -2.1186 × 10 ^-8
[Variable interval]
Wide angle end Intermediate focal length Telephoto end f 4.7600 10.8950 16.8301
d8 1.2174 6.2820 8.0585
d13 7.8909 2.8265 1.0500
d19 6.9417 3.3531 1.1000
d24 5.7090 9.2974 11.5506
Bf 0.5999 0.6000 0.6001
[Conditional value]
nd1 = 1.94594
nd2 = 1.94594
νd1 = 17.98
νd2 = 17.98
L1 = 5.500
Lp = 10.000
fw = 4.76001
f1 = 14.004786
f2 = −6.74050
ndp = 1.88300
Conditional expression (1) nd1 = 1.94594
Conditional expression (2) nd2 = 1.94594
Conditional expression (3) nd1 / nd2 = 1.000
Conditional expression (4) νd1 = 17.98
Conditional expression (5) νd2 = 17.98
Conditional expression (6) νd1 / νd2 = 1.000
Conditional expression (7) L1 / Lp = 0.550
Conditional expression (8) f1 / (− f2) = 2.084
Conditional expression (9) (-f2) /fw=1.416
Conditional expression (10) ndp = 1.88300

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied. Further, L1 = 5.500 with respect to Lp = 10.000, and it can be seen that L1 can be made smaller than the conventional one.

  9 to 11 are graphs showing various aberrations of the second example with respect to the d-line (λ = 587.6 nm). That is, FIG. 9 is a diagram of various aberrations in the infinite focus state in the wide-angle end state (f = 4.76 mm), and FIG. 10 is the infinite focus state in the intermediate focal length state (f = 10.90 mm). FIG. 11 is a diagram of various aberrations in the infinitely focused state in the telephoto end state (f = 16.83 mm). As is apparent from the respective aberration diagrams, in the second example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. FIG. 12 is a diagram illustrating a configuration of a zoom lens according to the third example. The zoom lens of the third embodiment has the same configuration as the zoom lens of the first embodiment except for the configuration of the second lens group and the aperture stop, and the same reference numerals are used for the respective parts as in the first embodiment. Detailed description will be omitted. The second lens group G2 of the third embodiment includes a biconcave negative lens L21 having an aspheric surface on the image side, a biconcave negative lens, and a convex surface on the object side, which are arranged in order from the object side. And a negative cemented lens L22 that is bonded to a positive meniscus lens. The aperture stop S of the third example is disposed closest to the object side of the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end to the telephoto end.

  Table 3 below shows specifications in the third embodiment. The surface numbers 1 to 28 in Table 3 correspond to the surfaces 1 to 28 in FIG. In the third embodiment, the lens surfaces of the seventh surface, the tenth surface, the fifteenth surface, and the twenty-first surface are formed in an aspherical shape.

(Table 3)
[Overall specifications]
Wide-angle end Intermediate focal length Telephoto end f = 4.76 to 10.90 to 16.83
F. NO = 3.61 ~ 4.48 ~ 5.31
2ω = 80.08 to 37.30 to 24.50
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number 1 18.6003 0.80 1.94594 17.98
2 9.1299 1.95
3 20.0061 0.80 1.94594 17.98
4 12.2378 1.95
5 0.0000 10.00 1.83400 37.16
6 0.0000 0.30
7 * 17.6318 2.59 1.77377 47.17
8 -17.0143 (d8)
9 -95.1601 0.80 1.85135 40.10
10 * 9.6243 1.05
11 −18.7968 0.80 1.81600 46.62
12 7.0462 1.31 1.94594 17.98
13 49.4372 (d13)
14 0.0000 0.50 (Aperture stop S)
15 * 5.7357 1.66 1.58913 61.25
16 −13.8410 0.20
17 27.9825 1.85 1.65160 58.55
18 -4.2034 0.80 1.83481 42.71
19 7.6543 (d19)
20 11.0138 2.15 1.60602 57.44
21 * −11.6568 0.20
22 6.7719 2.05 1.49700 81.54
23 43.7568 0.80 1.92286 20.88
24 6.2063 (d24)
25 0.0000 0.55 1.54437 70.51
26 0.0000 0.40
27 0.0000 0.50 1.51633 64.14
28 0.0000 (Bf)
[Aspherical data]
Surface number Κ C4 C6 C8 C10
7 -3.5829 + 3.1195 × 10 ^-5 -6.5188 × 10 ^-7 + 8.6095 × 10 ^-10 + 4.2745 × 10 ^-11
10 -9.0000 + 1.3893 × 10 ^-3 -3.2887 × 10 ^-5 -2.9925 × 10 ^-7 + 1.1579 × 10 ^-7
15 +0.1967 +5.0 256 × 10 ^-5 + 6.1634 × 10 ^-6 + 2.2998 × 10 ^-6 -1.2189 × 10 ^-7
21 +0.6898 + 3.7981 × 10 ^-4 + 7.2724 × 10 ^-6 -9.6564 × 10 ^-8 -5.0538 × 10 ^-9
[Variable interval]
Wide angle end Intermediate focal length Telephoto end f 4.7600 10.8950 16.8300
d8 1.2203 6.3686 8.2935
d13 8.1217 2.9734 1.0485
d19 6.7033 3.1869 1.1000
d24 5.8354 9.3517 11.4386
Bf 0.6000 0.6000 0.6000
[Conditional value]
nd1 = 1.94594
nd2 = 1.94594
νd1 = 17.98
νd2 = 17.98
L1 = 5.500
Lp = 10.000
fw = 4.76000
f1 = 14.009358
f2 = −6.74689
ndp = 1.83400
Conditional expression (1) nd1 = 1.94594
Conditional expression (2) nd2 = 1.94594
Conditional expression (3) nd1 / nd2 = 1.000
Conditional expression (4) νd1 = 17.98
Conditional expression (5) νd2 = 17.98
Conditional expression (6) νd1 / νd2 = 1.000
Conditional expression (7) L1 / Lp = 0.550
Conditional expression (8) f1 / (− f2) = 2.089
Conditional expression (9) (− f2) /fw=1.417
Conditional expression (10) ndp = 1.83400

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied. Further, L1 = 5.500 with respect to Lp = 10.000, and it can be seen that L1 can be made smaller than the conventional one.

  13 to 15 are graphs showing various aberrations of the third example with respect to the d-line (λ = 587.6 nm). That is, FIG. 13 is a diagram of various aberrations in the infinite focus state in the wide-angle end state (f = 4.76 mm), and FIG. 14 is the infinite focus state in the intermediate focal length state (f = 10.90 mm). FIG. 15 is a diagram of various aberrations in the infinitely focused state in the telephoto end state (f = 16.83 mm). As is apparent from the respective aberration diagrams, in the third example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Fourth embodiment)
Hereinafter, a fourth embodiment of the present application will be described with reference to FIGS. 16 to 19 and Table 4. FIG. FIG. 16 is a diagram illustrating a configuration of a zoom lens according to the fourth example. The zoom lens of the fourth embodiment has the same configuration as the zoom lens of the first embodiment except for the configuration of the second lens group, and the same reference numerals as those in the first embodiment are given to the respective parts. Detailed description is omitted. The second lens group G2 of the fifth example includes a biconcave negative lens L21 having an aspheric surface on the image side, which is arranged in order from the object side, a biconcave negative lens, and a biconvex positive lens. It comprises a negative cemented lens L22 bonded with a lens.

  Table 4 below shows specifications in the fourth embodiment. The surface numbers 1 to 28 in Table 4 correspond to the surfaces 1 to 28 in FIG. In the fourth embodiment, the lens surfaces of the seventh surface, the tenth surface, the fourteenth surface, and the twenty-first surface are formed in an aspherical shape.

(Table 4)
[Overall specifications]
Wide angle end Intermediate focal length Telephoto end f = 4.76 to 10.83 to 16.83
F. NO = 3.69 to 4.63 to 5.63
2ω = 80.12 to 37.46 to 24.50
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number 1 24.0157 0.80 1.94594 17.98
2 8.8935 1.93
3 21.2986 0.80 2.00069 25.46
4 16.1029 1.50
5 0.0000 9.60 1.88300 40.76
6 0.0000 0.30
7 * 19.6885 2.55 1.77377 47.17
8 -16.7162 (d8)
9 -71.9418 0.80 1.85135 40.10
10 * 9.2063 1.22
11 −14.8404 0.80 1.81600 46.62
12 10.8518 1.31 1.94594 17.98
13-67.4208 (d13)
14 * 5.9953 1.45 1.58913 61.25
15 -36.9608 0.50
16 0.0000 0.50 (Aperture stop S)
17 13.8168 1.85 1.64000 60.08
18 −4.0035 0.80 1.83481 42.71
19 8.2259 (d19)
20 11.9130 2.09 1.58913 61.25
21 * -11.2129 0.20
22 5.9451 2.05 1.49700 81.54
23 64.9268 0.80 1.84666 23.78
24 5.6786 (d24)
25 0.0000 0.55 1.54437 70.51
26 0.0000 0.40
27 0.0000 0.50 1.51633 64.14
28 0.0000 (Bf)
[Aspherical data]
Surface number Κ C4 C6 C8 C10
7 -3.6294 + 1.6073 × 10 ^-5 -4.6863 × 10 ^-7 + 4.0036 × 10 ^-9 -2.0969 × 10 ^-11
10 -9.0000 + 1.5122 × 10 ^-3 -5.1954 × 10 ^-5 + 1.0103 × 10 ^-6 + 3.8507 × 10 ^-8
14 +0.4518 + 1.7174 × 10 ^-4 + 1.9840 × 10 ^-5 + 1.6119 × 10 ^-8 + 4.3659 × 10 ^-8
21 +6.5379 + 8.9943 × 10 ^-4 + 2.2966 × 10 ^-5 -4.2505 × 10 ^-7 + 8.1325 × 10 ^-8
[Variable interval]
Wide angle end Intermediate focal length Telephoto end f 4.7600 10.8344 16.8300
d8 1.2428 7.0385 9.0846
d13 8.8916 3.0958 1.0500
d19 6.9489 3.3971 1.1000
d24 5.5049 9.0566 11.3537
Bf 0.5998 0.5999 0.5998
[Conditional value]
nd1 = 1.94594
nd2 = 2.00069
νd1 = 17.98
νd2 = 2.46
L1 = 5.034
Lp = 9.600
fw = 4.75998
f1 = 15.92586
f2 = −7.44907
ndp = 1.88300
Conditional expression (1) nd1 = 1.94594
Conditional expression (2) nd2 = 2.00069
Conditional expression (3) nd1 / nd2 = 0.993
Conditional expression (4) νd1 = 17.98
Conditional expression (5) νd2 = 2.46
Conditional expression (6) νd1 / νd2 = 0.706
Conditional expression (7) L1 / Lp = 0.524
Conditional expression (8) f1 / (− f2) = 2.138
Conditional expression (9) (-f2) /fw=1.565
Conditional expression (10) ndp = 1.88300

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied. Further, L1 = 5.034 with respect to Lp = 9.600, and it can be seen that L1 can be made smaller than the conventional one.

  17 to 19 are graphs showing various aberrations of the fourth example with respect to the d-line (λ = 587.6 nm). That is, FIG. 17 is a diagram of various aberrations in the infinite focus state in the wide-angle end state (f = 4.76 mm), and FIG. 18 is the infinite focus state in the intermediate focal length state (f = 10.83 mm). FIG. 19 is a diagram of various aberrations in the infinitely focused state in the telephoto end state (f = 16.83 mm). As is apparent from the respective aberration diagrams, in the fourth example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(5th Example)
Hereinafter, a fifth embodiment of the present application will be described with reference to FIGS. 20 to 23 and Table 5. FIG. FIG. 20 is a diagram illustrating a configuration of a zoom lens according to Example 5. The zoom lens of the fifth example has the same configuration as that of the zoom lens of the first example except for the configurations of the second lens group and the fourth lens group, and each part has the same configuration as that of the first example. Reference numerals are assigned and detailed description is omitted. The second lens group G2 of the fifth example includes a biconcave negative lens L21 having an aspheric surface on the image side, which is arranged in order from the object side, a biconcave negative lens, and a biconvex positive lens. It comprises a negative cemented lens L22 bonded with a lens. The fourth lens group G4 of the fifth example includes a biconvex positive lens L41 having an aspheric surface on the image side, arranged in order from the object side, a biconvex positive lens, and a biconcave negative lens. And a negative cemented lens L42.

  Table 5 below shows specifications in the fifth embodiment. The surface numbers 1 to 28 in Table 5 correspond to the surfaces 1 to 28 in FIG. In the fifth embodiment, the seventh, tenth, fourteenth, and twenty-first surfaces are formed in an aspheric shape.

(Table 5)
[Overall specifications]
Wide angle end Intermediate focal length Telephoto end f = 4.76 to 10.83 to 19.20
F. NO = 3.47 to 4.34 to 5.75
2ω = 80.20 to 37.30 to 21.54
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number 1 17.2732 0.80 1.94594 17.98
2 8.3539 2.29
3 22.2424 0.80 2.00069 25.46
4 14.8265 1.60
5 0.0000 8.80 1.88300 40.76
6 0.0000 0.30
7 * 19.9314 2.56 1.76802 49.24
8 -16.242 (d8)
9 -21.2094 0.80 1.85135 40.10
10 * 9.8366 1.00
11 −34.3738 0.80 1.83481 42.71
12 7.9969 1.47 1.94594 17.98
13 −1158.0055 (d13)
14 * 6.6673 1.51 1.59201 67.05
15 -28.2642 0.50
16 0.0000 0.50 (Aperture stop S)
17 11.6221 1.85 1.64000 60.08
18 -4.6955 0.80 1.88300 40.76
19 8.8567 (d19)
20 9.5123 2.50 1.59201 67.05
21 * −12.9644 0.20
22 7.1445 2.15 1.49700 81.54
23 -85.6130 0.80 1.79504 28.54
24 5.8608 (d24)
25 0.0000 0.60 1.54437 70.51
26 0.0000 0.40
27 0.0000 0.50 1.51633 64.14
28 0.0000 (Bf)
[Aspherical data]
Surface number Κ C4 C6 C8 C10
7 -7.6332 + 8.1356 × 10 ^-5 -1.1855 × 10 ^-6 + 1.0910 × 10 ^-8 -6.9554 × 10 ^-11
10 -9.0000 + 1.1174 × 10 ^-3 -4.2945 × 10 ^-5 + 1.3369 × 10 ^-6 -3.3511 × 10 ^-9
14 +0.4936 + 1.6354 × 10 ^-4 + 5.3401 × 10 ^-6 + 9.8630 × 10 ^-7 -2.7231 × 10 ^-8
21 +2.0477 + 5.2136 × 10 ^-4 + 6.2688 × 10 ^-7 + 2.6776 × 10 ^-7 -1.2539 × 10 ^-8
[Variable interval]
Wide angle end Intermediate focal length Telephoto end f 4.7600 10.8344 19.2000
d8 1.2308 7.1168 9.5209
d13 9.3400 3.4541 1.0500
d19 8.5106 4.5925 1.1000
d24 5.2744 9.1924 12.6849
Bf 0.5999 0.6000 0.6000
[Conditional value]
nd1 = 1.94594
nd2 = 2.000694
νd1 = 17.98
νd2 = 2.46
L1 = 5.498
Lp = 8.800
fw = 4.75999
f1 = 16.335427
f2 = −7.24275
ndp = 1.88300
Conditional expression (1) nd1 = 1.94594
Conditional expression (2) nd2 = 2.000694
Conditional expression (3) nd1 / nd2 = 0.993
Conditional expression (4) νd1 = 17.98
Conditional expression (5) νd2 = 25.46
Conditional expression (6) νd1 / νd2 = 0.706
Conditional expression (7) L1 / Lp = 0.625
Conditional expression (8) f1 / (− f2) = 2.258
Conditional expression (9) (-f2) /fw=1.522
Conditional expression (10) ndp = 1.88300

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied. Further, L1 = 5.498 with respect to Lp = 8.800, and it can be seen that L1 can be made smaller than the conventional one.

  21 to 23 are graphs showing various aberrations of the fifth example with respect to the d-line (λ = 587.6 nm). That is, FIG. 21 is a diagram of various aberrations in the infinite focus state in the wide-angle end state (f = 4.76 mm), and FIG. 22 is the infinite focus state in the intermediate focal length state (f = 10.83 mm). FIG. 23 is a diagram of various aberrations in the infinitely focused state in the telephoto end state (f = 19.20 mm). As is apparent from the respective aberration diagrams, in the fourth example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

  In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

  In each of the above-described embodiments, the four-group configuration is shown as the zoom lens. It is also possible to add another lens group between each lens group, or to add another lens group adjacent to the image side or the object side of the zoom lens system.

  In addition, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. This focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like). In particular, in the case of a four-group configuration, it is preferable that the second or fourth lens group is a focusing lens group.

  Alternatively, the lens group or the partial lens group may be vibrated in a direction perpendicular to the optical axis to correct the image blur caused by camera shake. In particular, the third lens group is preferably an anti-vibration lens group, but may be a second lens group.

  Each lens surface may be an aspherical surface. At this time, any one of an aspheric surface by grinding, a glass mold aspheric surface in which glass is formed into an aspheric shape by a mold, and a composite aspheric surface in which resin is formed in an aspheric shape on the surface of the glass may be used.

  The aperture stop is preferably disposed in the vicinity of the third lens group (the lens group including the shift lens group) or in the third lens group. However, the aperture stop is not provided and a lens frame is not provided. You may substitute that role.

  Further, each lens surface is provided with an antireflection film having a high transmittance in a wide wavelength range, thereby reducing flare and ghost and achieving high optical performance with high contrast.

  In addition, in order to explain the present invention in an easy-to-understand manner, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

(A) is a front view of a digital still camera, (b) is a rear view of a digital still camera. It is sectional drawing along arrow II-II in FIG. It is explanatory drawing which shows refractive power arrangement | positioning of a zoom lens. It is sectional drawing which shows the structure of the zoom lens which concerns on 1st Example. It is an aberration diagram in the wide-angle end state in the infinity in-focus state in the first example. FIG. 6 is a diagram illustrating various aberrations in the intermediate focal length state in the infinitely focused state in the first example. FIG. 6 is a diagram illustrating various aberrations in the telephoto end state at the infinity in-focus state in the first example. It is sectional drawing which shows the structure of the zoom lens which concerns on 2nd Example. FIG. 12 is a diagram illustrating various aberrations in the wide-angle end state at the infinity in-focus state in the second example. FIG. 12 is a diagram illustrating various aberrations in the intermediate focal length state in the infinitely focused state in the second example. FIG. 12 is a diagram illustrating various aberrations in the telephoto end state at the infinity in-focus state in the second example. It is sectional drawing which shows the structure of the zoom lens which concerns on 3rd Example. It is an aberration diagram in the wide-angle end state in the infinity in-focus state in the third example. FIG. 12 is a diagram illustrating various aberrations in the intermediate focal length state in the infinitely focused state in the third example. It is an aberration diagram in the telephoto end state of the infinity in-focus state in the third embodiment. It is sectional drawing which shows the structure of the zoom lens which concerns on 4th Example. It is various aberrational figures in the wide-angle end state of an infinite focus state in 4th Example. FIG. 11 is a diagram illustrating various aberrations in the intermediate focal length state in the infinitely focused state in the fourth example. FIG. 12 is a diagram illustrating various aberrations in the telephoto end state at the infinity in-focus state in the fourth example. It is sectional drawing which shows the structure of the zoom lens which concerns on 5th Example. It is various aberrational figures in the wide-angle end state of an infinite focus state in 5th Example. FIG. 12 is a diagram illustrating various aberrations in the intermediate focal length state at the infinity in-focus state in the fifth example. It is various aberrational figures in the telephoto end state of the infinity in-focus state in 5th Example.

Explanation of symbols

CAM digital still camera (optical equipment)
ZL zoom lens G1 first lens group G2 second lens group G3 third lens group G4 fourth lens group P optical path bending element I image plane

Claims (17)

In a zoom lens configured with a plurality of lens groups arranged in order from the object side along the optical axis,
The first lens group arranged closest to the object side among the plurality of lens groups has a positive refractive power, an optical path bending element that bends the optical path, and a plurality of lenses disposed on the object side relative to the optical path bending element. Has
The plurality of lenses include at least one negative lens having a refractive index with respect to d-line exceeding 1.90 ,
The second lens group arranged on the image side of the first lens group among the plurality of lens groups has a negative refractive index,
When the focal length of the entire lens system in the wide-angle end state is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2,
1.9 <f1 / (− f2) <2.5
1.2 <(− f2) / fw <1.8
A zoom lens that satisfies the following conditions . When the refractive index for the d-line of the negative lens closest to the object among the plurality of lenses is nd1, the following formula nd1> 1.90.
When the refractive index for the d-line of the most negative lens on the image side among the plurality of lenses is nd2, the following formula nd2> 1.90 is satisfied.
The zoom lens according to claim 1, wherein the following condition is satisfied. The zoom lens according to claim 1, wherein the plurality of lenses are two lenses. When the refractive index with respect to the d-line of the negative lens closest to the object among the plurality of lenses is nd1, and the refractive index with respect to the d-line of the negative lens closest to the image among the plurality of lenses is nd2, the following expression 0. 7 <nd1 / nd2 <1.1
4. The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. When the Abbe number for the d-line of the negative lens closest to the object among the plurality of lenses is νd1, the following equation νd1 <50
When the Abbe number for the d-line of the negative lens closest to the image among the plurality of lenses is νd2, the following equation is satisfied: νd2 <50
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. Wherein the plurality of the Abbe number at the d-line of the negative lens on the most object side of the lens is vd1, when the Abbe number νd2 the d-line of the negative lens on the most image side among the plurality of lenses, the following equation 0. 4 <νd1 / νd2 <1.3
The zoom lens according to any one of claims 1 to 5, wherein the following condition is satisfied. The optical path bending element is a prism;
When the distance on the optical axis from the most object side surface in the first lens group to the prism is L1, and the distance on the optical axis of the prism is Lp, the following equation is given: L1 / Lp <1.0
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. The optical path bending element is a prism;
When the refractive index for the d-line of the prism is ndp, the following formula ndp> 1.80
The zoom lens according to claim 1 , wherein the zoom lens satisfies the following condition. The plurality of lens groups includes the first lens group, the second lens group, the third lens group, and the fourth lens group, which are arranged in order from the object side along the optical axis. The zoom lens according to any one of claims 1 to 8 . Claims wherein the second lens group has a negative refractive power, the third lens group has a positive refractive power, wherein the fourth lens group has a positive refractive power The zoom lens according to 9 . The first lens group and the third lens group are fixed during zooming from the wide-angle end to the telephoto end,
11. The zoom lens according to claim 9, wherein the second lens group and the fourth lens group move along an optical axis during zooming from the wide-angle end to the telephoto end. The zoom lens according to any one of claims 1 to 11 , wherein the plurality of lenses include negative meniscus lenses having convex surfaces facing the object side. The zoom lens according to any one of claims 1 to 12 , wherein the first lens group includes a positive lens disposed on the image side of the optical path bending element. . Wherein the first lens group zoom lens according to any one of claims 13 claim 1, characterized in that it is configured with aspheric lens. The zoom lens according to any one of claims 1 to 14 , wherein the angle of view in the wide-angle end state is 75 degrees or more. In an optical apparatus having a zoom lens that forms an image of an object on a predetermined surface,
An optical apparatus, wherein the zoom lens is the zoom lens according to any one of claims 1 to 15 . An imaging method for forming an image of the object on a predetermined plane using a zoom lens having a plurality of lens groups arranged in order from the object side along the optical axis,
The first lens group arranged closest to the object side among the plurality of lens groups has a positive refractive power,
The first lens group is provided with an optical path bending element that bends the optical path, and a plurality of lenses are arranged closer to the object side than the optical path bending element,
Including a plurality of lenses including at least one negative lens having a refractive index with respect to d-line exceeding 1.90 ;
A second lens group arranged on the image side of the first lens group among the plurality of lens groups has a negative refractive index;
When the focal length of the entire lens system in the wide-angle end state is fw, the focal length of the first lens group is f1, and the focal length of the second lens group is f2,
1.9 <f1 / (− f2) <2.5
1.2 <(− f2) / fw <1.8
An imaging method characterized by satisfying the above condition .

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