JP7105852B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens particularly suitable for imaging devices such as digital cameras, interchangeable lens digital cameras, movie cameras, etc., and to an imaging device equipped with this zoom lens.

2. Description of the Related Art Patent Documents 1 to 3 disclose zoom lenses used in imaging devices such as digital cameras, interchangeable lens digital cameras, and movie cameras.

JP 2015-121768 A JP 2014-77867 A JP-A-2015-4880

A zoom lens used in the imaging apparatus is required to be small and light in order to improve portability. There is also a demand for high-speed focusing, good optical performance over all shooting distances, and a wider angle of view at the wide-angle end.

However, in the zoom lenses disclosed in Patent Documents 1 and 2, the lens group closest to the object side (first lens group) is large while achieving a wide angle of view and high-speed focusing, and compactness is sufficiently achieved. It cannot be said that it is.

Further, in the zoom lens disclosed in Patent Document 3, it cannot be said that it is possible to achieve both reduction in size and high-speed focusing and suppression of aberration fluctuations due to photographing distance.

The present invention has been made in view of the above circumstances, and is a zoom lens that is compact and lightweight as a whole, enables high-speed focusing, reduces aberration fluctuations depending on the object distance, and provides high optical performance over the entire object distance. , and an imaging apparatus equipped with this zoom lens.

The zoom lens of the present invention comprises, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a positive lens group. and a fourth lens group having refractive power. During zooming, the first, second, third, and fourth lens groups change the distances between adjacent groups in the optical axis direction. , the third lens group consists of a negative lens, during focusing, only the third lens group moves along the optical axis, the second lens group has an aperture, the second lens group has the optical axis and It has a vibration reduction lens group that performs vibration reduction by moving in an orthogonal direction, the vibration reduction lens group is arranged on the image side of the diaphragm, and the fourth lens group is fixed during zooming. The four lens groups consist of positive lenses, with Bf as the back focus at the wide-angle end, IH as the maximum image height , ft as the focal length of the entire system when focused on an object at infinity at the telephoto end, and ft as the focal length of the anti-vibration lens group. fois , the following conditional expressions ( 4 ) and (6) are satisfied.
0.6<Bf/IH <1.2 ( 4 )
0.5<ft/fois<2 (6)

The second lens group preferably has lenses adjacent to the object side and image side of the stop . In this case, the second lens group preferably has a positive lens and a diaphragm in succession from the object side.

Moreover, it is preferable that the second lens group has a cemented lens composed of at least one positive lens and at least one negative lens on the image side of the stop.

In this case, the cemented lens is composed of one positive lens and one negative lens, and if the Abbe number difference between the positive lens and the negative lens constituting the cemented lens is Δνcd, the following conditional expression (8) is satisfied. It is preferable that the following conditional expression (8-1) is satisfied .
15<Δνcd<60 (8)
20<Δνcd<50 (8-1)

The zoom lens of the present invention preferably satisfies the following conditional expression (4-3).
0.6<Bf/IH≦0.76 (4-3)

An imaging apparatus of the present invention includes the zoom lens of the present invention described above.

In addition, the above "consisting of" includes, in addition to those listed as constituent elements, lenses that have substantially no power, optical elements other than lenses such as diaphragms, masks, cover glasses and filters, lens flanges, lenses It is contemplated that the barrel, imaging device, mechanical parts such as an anti-shake mechanism, etc., may also be included.

Also, the refractive index and Abbe number in each conditional expression use the d-line as a reference wavelength.

Also, the surface shape, the sign of the refractive power, and the radius of curvature of the lens described above are considered in the paraxial region when an aspherical surface is included.

The first and second zoom lenses of the present invention are composed of, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power. It consists of a lens group and a fourth lens group having a positive refractive power. During zooming, the first lens group, the second lens group, the third lens group, and the fourth lens group are aligned with the optical axes of the adjacent groups. The first lens group consists of, in order from the object side, a first lens with negative refractive power, a second lens with negative refractive power, and a third lens with positive refractive power. The third lens group consists of a negative lens, and only the third lens group moves along the optical axis during focusing, satisfying a predetermined conditional expression. In addition, it is possible to provide a zoom lens that enables high-speed focusing, has little variation in aberrations depending on the object distance, and provides high optical performance over the entire object distance, and an imaging apparatus equipped with this zoom lens.

FIG. 2 is a cross-sectional view showing the lens configuration of the zoom lenses according to the first and second embodiments of the present invention (common with Example 1); FIG. 2 is a cross-sectional view showing the lens configuration of a zoom lens according to Example 2 of the present invention; FIG. 3 is a cross-sectional view showing the lens configuration of a zoom lens according to Example 3 of the present invention; FIG. 4 is a cross-sectional view showing the lens configuration of a zoom lens according to Example 4 of the present invention; FIG. 5 is a cross-sectional view showing the lens configuration of a zoom lens according to Example 5 of the present invention; Aberration diagrams of the zoom lens according to Example 1 of the present invention when focusing on an object at infinity. Aberration diagrams of the zoom lens according to Example 1 of the present invention when focusing on a finite distance object. Aberration diagrams of the zoom lens according to Example 2 of the present invention when focusing on an object at infinity. Aberration diagrams of the zoom lens of Example 2 of the present invention when focusing on a finite distance object Aberration diagrams of the zoom lens according to Example 3 of the present invention when focusing on an object at infinity Aberration diagrams of the zoom lens of Example 3 of the present invention when focusing on a finite distance object Aberration diagrams of the zoom lens of Example 4 of the present invention when focusing on an object at infinity Aberration diagrams of the zoom lens of Example 4 of the present invention when focusing on a finite distance object Aberration diagrams of the zoom lens of Example 5 of the present invention when focusing on an object at infinity Aberration diagrams of the zoom lens of Example 5 of the present invention when focusing on a finite distance object 1 is a perspective view showing the front side of an imaging device according to an embodiment of the present invention; FIG. FIG. 16 is a perspective view showing the rear side of the imaging device of FIG. 16

A first embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the lens configuration of the zoom lens according to the first embodiment of the invention. The configuration example shown in FIG. 1 is common to the configuration of the zoom lens of Example 1, which will be described later. In FIG. 1, the left side is the object side, and the right side is the image side.

In FIG. 1, the upper part labeled WIDE shows the state of the wide-angle end, the axial luminous flux wa and the luminous flux wb at the maximum angle of view are entered as the luminous flux, and the lower part labeled TELE shows the state of the telephoto end, and the luminous flux , the on-axis luminous flux ta and the luminous flux tb at the maximum angle of view are entered. All of these show a state in which an object at an infinite distance is in focus. In addition, the locus of movement of each lens group during zooming is also entered.

When the zoom lens is mounted on an imaging device, it is preferable to include various filters and/or a protective cover glass according to the specifications of the imaging device. 2 shows an example in which the optical member PP of is arranged between the lens system and the image plane Sim. However, the position of the optical member PP is not limited to that shown in FIG. 1, and a configuration in which the optical member PP is omitted is also possible.

The zoom lens of this embodiment comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. and a fourth lens group G4 having a positive refractive power. During zooming, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 are adjacent to each other. are configured to change the interval in the optical axis Z direction. By giving the first lens group G1 closest to the object side a negative refractive power in this manner, divergent light is incident on the subsequent lens group, which is advantageous in ensuring the amount of peripheral light. Also, by giving the third lens group G3 a negative refractive power, the luminous flux can be made smaller, which is advantageous in reducing the diameter.

The first lens group G1 consists of, in order from the object side, a first lens L1a having negative refractive power, a second lens L1b having negative refractive power, and a third lens L1c having positive refractive power. Bringing the entrance pupil closer to the object side with the first lens L1a having negative refractive power contributes to securing the angle of view at the wide-angle end and reducing the diameter. Further, by continuously arranging the second lens L1b having negative refractive power and the third lens L1c having positive refractive power, spherical aberration at the telephoto end is suppressed, and the entire first lens group G1 Aberration fluctuations during zooming can be suppressed.

The third lens group G3 is composed of a negative lens L3a, and is constructed so that only the third lens group G3 moves along the optical axis Z during focusing. That is, the third lens group G3 functions as a focusing lens group FOCUS. Such a configuration contributes to reduction in size and weight of the focusing unit (focusing lens group FOCUS and a mechanism for moving this focusing lens group FOCUS) and high-speed autofocusing.

Furthermore, the refractive index of the first lens L1a is Nd1, the Abbe number of the first lens L1a is νd1, the refractive index of the third lens L1c is Nd3, the Abbe number of the third lens L1c is νd3, and focusing on an object at infinity at the wide-angle end. When fW is the focal length of the entire system at time, f3 is the focal length of the third lens group G3, Bf is the back focus, and IH is the maximum image height, the conditional expressions (1) to (4) are satisfied. It is
1.7<Nd1−0.0037×νd1<2 (1)
1.8<Nd3−0.0037×νd3<2 (2)
−0.6<fw/f3<−0.15 (3)
0.6<Bf/IH<1.2 (4)

If the upper limit of conditional expression (1) is not exceeded, it is advantageous for correction of chromatic aberration. Keeping the value below the lower limit of conditional expression (1) is advantageous for miniaturization and weight reduction. If the conditional expression (1-1) is satisfied, better characteristics can be obtained.
1.75<Nd1−0.0037×νd1<2 (1−1)

If the upper limit of conditional expression (2) is not exceeded, it is advantageous for correction of chromatic aberration. Keeping the value below the lower limit of conditional expression (2) is advantageous for miniaturization and weight reduction. If the conditional expression (2-1) is satisfied, better characteristics can be obtained.
1.85<Nd3−0.0037×νd3<2 (2-1)

By not exceeding the upper limit of conditional expression (3), it is possible to prevent the refractive power of the third lens group G3 from becoming too weak. advantageous for conversion. Abiding by the lower limit of conditional expression (3) prevents the refracting power of the third lens group G3 from becoming too strong, which is advantageous for suppressing aberration fluctuations during focusing. If the conditional expression (3-1) is satisfied, better characteristics can be obtained.
-0.5<fw/f3<-0.2 (3-1)

Keeping the upper limit of conditional expression (4) below is advantageous for downsizing. In addition, it is advantageous in suppressing the incident angle of the chief ray of the off-axis ray to the image plane Sim on the wide-angle side. Abiding by the lower limit of conditional expression (4) prevents the zoom lens from becoming too close to the image plane Sim, which is advantageous for reducing the diameter of the lens. If the conditional expression (4-1) is satisfied, better characteristics can be obtained.
0.7<Bf/IH<1.1 (4-1)

Next, a second embodiment of the invention will be described. The lens configuration of the zoom lens according to the second embodiment is the same as that of the zoom lens according to the first embodiment shown in FIG.

The zoom lens of this embodiment comprises, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power. and a fourth lens group G4 having a positive refractive power. During zooming, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 are adjacent to each other. are configured to change the interval in the optical axis Z direction.

The first lens group G1 consists of, in order from the object side, a first lens L1a having negative refractive power, a second lens L1b having negative refractive power, and a third lens L1c having positive refractive power. The third lens group G3 is composed of a negative lens L3a, and is constructed so that only the third lens group G3 moves along the optical axis Z during focusing.

Furthermore, the refractive index of the first lens L1a is Nd1, the Abbe number of the first lens L1a is νd1, the refractive index of the third lens L1c is Nd3, the Abbe number of the third lens L1c is νd3, and focusing on an object at infinity at the wide-angle end. When the focal length of the entire system at time is fW, the focal length of the third lens group G3 is f3, the back focus is Bf, and the focal length of the fourth lens group G4 is f4, conditional expressions (1) to (3), It is configured to satisfy (5).
1.7<Nd1−0.0037×νd1<2 (1)
1.8<Nd3−0.0037×νd3<2 (2)
−0.6<fw/f3<−0.15 (3)
0.15<Bf/f4<0.35 (5)

Compared to the zoom lens according to the first embodiment, the zoom lens according to the second embodiment is configured to satisfy conditional expression (5) instead of conditional expression (4). are the same. Therefore, explanations other than conditional expression (5) are omitted.

By not exceeding the upper limit of conditional expression (5), it is possible to prevent the back focus from becoming too long or the refractive power of the fourth lens group G4 from becoming too strong. Since it is possible to prevent the negative refractive power of the group G3 from becoming too strong, this is advantageous in suppressing aberration fluctuations during focusing. By ensuring that the lower limit of conditional expression (5) is not exceeded, it is possible to prevent the back focus from becoming too short or the refractive power of the fourth lens group G4 from becoming too weak. Since the negative refractive power of the group G3 can be prevented from becoming too weak, the amount of movement of the third lens group G3 during focusing can be suppressed, which is advantageous for downsizing. If the conditional expression (5-1) is satisfied, better characteristics can be obtained.
0.18<Bf/f4<0.3 (5-1)

In the zoom lenses of the first and second embodiments, the second lens group G2 has an anti-vibration lens group OIS that performs anti-vibration by moving in a direction perpendicular to the optical axis Z. If the focal length of the entire system during object focusing is ft, and the focal length of the anti-vibration lens group OIS is fois, it is preferable to satisfy conditional expression (6). By not exceeding the upper limit of conditional expression (6), it is possible to prevent the refractive power of the anti-vibration lens group OIS from becoming too strong, so that aberration fluctuations during anti-vibration can be reduced. By ensuring that the conditional expression (6) does not fall below the lower limit, it is possible to prevent the amount of movement of the anti-vibration lens group OIS from becoming too large. It is possible to reduce the size of the OIS and the mechanism for moving the vibration reduction lens group OIS. If the conditional expression (6-1) is satisfied, better characteristics can be obtained.
0.5<ft/fois<2 (6)
1<ft/fois<1.5 (6-1)

Further, the second lens group G2 has an anti-vibration lens group OIS that performs anti-vibration by moving in a direction orthogonal to the optical axis Z, and the anti-vibration lens group OIS preferably consists of one lens. . Such a configuration is advantageous for reducing the size and weight of the anti-vibration unit.

In this case, it is preferable to satisfy the conditional expression (7), where νud is the Abbe number of the lenses constituting the vibration reduction lens group OIS. A material having a sufficient refractive index can be selected by ensuring that the upper limit of conditional expression (7) is not exceeded. Abiding by the lower limit of conditional expression (7) is advantageous for suppressing fluctuations in chromatic aberration during vibration reduction. If the conditional expression (7-1) is satisfied, better characteristics can be obtained.
50<νud<100 (7)
55<νud<95 (7-1)

The second lens group G2 preferably has an aperture stop St and has lenses adjacent to the object side and image side of the aperture stop St. By adopting such a configuration, it is easy to secure the amount of movement of the second lens group G2 at the time of zooming, and it is also advantageous for miniaturization.

In this case, the second lens group G2 preferably has a positive lens and an aperture stop St in succession from the object side. Arranging the positive lens on the object side of the aperture stop St in this manner is advantageous in reducing the diameter of the aperture stop St.

Also, the second lens group G2 preferably has a cemented lens composed of at least one positive lens and at least one negative lens on the image side of the aperture stop St. Such a configuration is advantageous for correction of longitudinal chromatic aberration.

In this case, the cemented lens consists of one positive lens and one negative lens, and the difference in Abbe number between the positive lens and the negative lens (the Abbe number of the positive lens - the Abbe number of the negative lens) that constitutes the cemented lens is When Δνcd, it is preferable to satisfy the conditional expression (8). By satisfying conditional expression (8), chromatic aberration in the second lens group G2 can be sufficiently corrected, which is advantageous for achieving high optical performance. If the conditional expression (8-1) is satisfied, better characteristics can be obtained.
15<Δνcd<60 (8)
20<Δνcd<50 (8-1)

Moreover, it is preferable that the fourth lens group G4 is composed of a positive lens. By adopting such a configuration, it is possible to improve the balance of aberration fluctuations during focusing with the third lens group G3, which is a negative lens, while securing the amount of movement of the third lens group G3 during focusing. can.

Further, the fourth lens group G4 may be fixed during zooming, or may be movable during zooming. If the fourth lens group G4 is fixed during zooming, dust can be prevented from entering the zoom lens. If the fourth lens group G4 is designed to move during zooming, it is advantageous for reducing the diameter of the fourth lens group G4.

Further, it is preferable that the surface of the first lens group G1 closest to the image side has a convex surface facing the object side. By adopting such a configuration, it becomes easier to secure the distance from the second lens group G2 at the telephoto end, and it is also advantageous for miniaturization.

In the example shown in FIG. 1, an example in which the optical member PP is arranged between the lens system and the image plane Sim is shown. These various filters may be placed between each lens instead of being placed between the image plane Sim, or the lens surface of one of the lenses may be coated with a coating having the same effect as the various filters. may

Numerical examples of the zoom lens of the present invention will now be described.

First, the zoom lens of Example 1 will be described. FIG. 1 is a sectional view showing the lens configuration of the zoom lens of Example 1. As shown in FIG. In FIG. 1 and FIGS. 2 to 5 corresponding to Examples 2 to 5 described later, the left side is the object side and the right side is the image side. The position on the optical axis Z is shown. The upper part labeled WIDE shows the state at the wide-angle end, and the axial luminous flux wa and the luminous flux wb at the maximum angle of view are entered as the luminous flux. Ta and the luminous flux tb at the maximum angle of view are entered. All of these show a state in which an object at an infinite distance is in focus. In addition, the locus of movement of each lens group during zooming is also entered.

The zoom lens of Example 1 is composed of, in order from the object side, a first lens group G1 composed of three lenses L1a to L1c, an aperture diaphragm St and five lenses L2a to L2e. a second lens group G2, a third lens group G3 consisting of only one lens L3a, and a fourth lens group G4 consisting of only one lens L4a. there is Also, during zooming, the first lens group G1, the second lens group G2, and the third lens group G3 move, and the fourth lens group G4 is fixed.

Table 1 shows basic lens data of the zoom lens of Example 1, Table 2 shows data on specifications, Table 3 shows data on varying surface spacing, and Table 4 shows data on aspheric coefficients. In the following, the meaning of the symbols in the table will be explained by taking the example 1 as an example, but the meanings of the examples 2 to 5 are basically the same.

In the lens data of Table 1, the surface number column indicates the surface number that increases sequentially toward the image plane side, with the surface of the component closest to the object side being the first, and the curvature radius column indicates the radius of curvature of each surface. , and the space between each surface and the next surface on the optical axis Z is shown in the space between surfaces. The n column shows the refractive index for the d-line (wavelength of 587.6 nm (nanometers)) of each optical element, and the ν column shows the d-line (wavelength of 587.6 nm (nanometers)) of each optical element. shows the Abbe number at

The sign of the radius of curvature is positive when the surface shape is convex toward the object side, and negative when the surface shape is convex toward the image plane side. The basic lens data also include the aperture diaphragm St and the optical member PP. In the surface number column of the surface corresponding to the aperture diaphragm St, the word (aperture) is described together with the surface number. In addition, in the lens data of Table 1, DD [surface number] is written in the column of the surface distance that changes during zooming and focusing. Numerical values corresponding to this DD [face number] are shown in Table 3.

The data on the specifications in Table 2 include the zoom magnification, focal length f', and back focus when focusing on an object at infinity and when focusing on a finite distance object (when focusing on an object at a distance of 1 m from the image plane). Bf', F number FNo. , indicates the value of the total angle of view 2ω (°).

In the lens data of Table 1, the surface number of the aspherical surface is marked with *, and the numerical value of the paraxial radius of curvature is shown as the radius of curvature of the aspherical surface. The data on the aspherical surface coefficients in Table 4 shows the surface numbers of the aspherical surfaces and the aspherical surface coefficients of these aspherical surfaces. "E±n" (n: integer) in the numerical values of the aspheric coefficients in Table 4 means "×10 ^±n ". The aspherical surface coefficients are the values of the respective coefficients KA and Am in the aspherical surface formula represented by the following formula.
Zd=C·h ² /{1+(1−KA·C ² ·h ² ) ^1/2 }+ΣAm·h ^m
however,
Zd: Depth of the aspherical surface (the length of the perpendicular drawn from the point on the aspherical surface with height h to the plane perpendicular to the optical axis where the aspherical vertex is in contact)
h: height (distance from optical axis)
C: reciprocal of paraxial radius of curvature KA, Am: coefficient of aspherical surface, and Σ in aspherical surface depth Zd means the summation with respect to m.

In the basic lens data, data on specifications, and data on variable surface spacing, degrees are used as units of angles and mm (millimeters) are used as units of length. Other suitable units can also be used as they can be used even when reduced.

FIG. 6 shows each aberration diagram of the zoom lens of Example 1 when focusing on an object at infinity, and FIG. 7 shows each aberration diagram when focusing on a finite distance object (when focusing on an object 1 m away from the image plane). show. 6 and 7, spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end (WIDE) are shown in order from the upper left side in FIGS. , and the spherical aberration, astigmatism, distortion, and chromatic aberration of magnification at the telephoto end (TELE) are shown in order from the lower left side in FIGS. . Each aberration chart showing spherical aberration, astigmatism, and distortion shows aberration with the d-line (wavelength 587.6 nm (nanometers)) as the reference wavelength. The spherical aberration diagram shows d-line (wavelength 587.6 nm (nanometers)), C-line (wavelength 656.3 nm (nanometers)), F-line (wavelength 486.1 nm (nanometers)), and g-line (wavelength 435 nm). .8 nm (nanometers)) are shown in solid, long dash, short dash, and gray solid lines, respectively. In the astigmatism diagram, aberrations in the sagittal and tangential directions are indicated by solid lines and short dashed lines, respectively. In the diagram of lateral chromatic aberration, aberrations for C-line (wavelength 656.3 nm (nanometers)), F-line (wavelength 486.1 nm (nanometers)), and g-line (wavelength 435.8 nm (nanometers)) are plotted. Dashed line, short dashed line, and solid gray line. It should be noted that FNo. means the F-number, and ω in other aberration diagrams means the half angle of view.

Next, the zoom lens of Example 2 will be described. FIG. 2 is a cross-sectional view showing the lens configuration of the zoom lens of Example 2. As shown in FIG. The group configuration of the zoom lens of Example 2 and the lens groups that move during zooming are the same as those of the zoom lens of Example 1. FIG. Table 5 shows the basic lens data of the zoom lens of Example 2, Table 6 shows the data on the specifications, Table 7 shows the data on the varying surface spacing, Table 8 shows the data on the aspheric coefficients, and Table 8 shows the FIG. 8 shows aberration diagrams during focusing, and FIG. 9 shows aberration diagrams during finite-distance object focusing (when focusing on an object at a distance of 1 m from the image plane).

Next, the zoom lens of Example 3 will be described. FIG. 3 is a cross-sectional view showing the lens configuration of the zoom lens of Example 3. As shown in FIG. The group configuration of the zoom lens of Example 3 and the lens groups that move during zooming are the same as those of the zoom lens of Example 1. FIG. Table 9 shows the basic lens data of the zoom lens of Example 3, Table 10 shows data on specifications, Table 11 shows data on changing surface spacing, Table 12 shows data on aspheric coefficients, and Table 12 shows data on infinite distance objects. FIG. 10 shows aberration diagrams during focusing, and FIG. 11 shows aberration diagrams during finite-distance object focusing (when focusing on an object at a distance of 1 m from the image plane).

Next, the zoom lens of Example 4 will be described. FIG. 4 is a sectional view showing the lens configuration of the zoom lens of Example 4. As shown in FIG. The group configuration of the zoom lens of Example 4 and the lens groups that move during zooming are the same as those of the zoom lens of Example 1. FIG. Table 13 shows the basic lens data of the zoom lens of Example 4, Table 14 shows the data on the specifications, Table 15 shows the data on the varying surface spacing, Table 16 shows the data on the aspheric coefficients, and Table 16 shows the FIG. 12 shows aberration diagrams during focusing, and FIG. 13 shows aberration diagrams during finite-distance object focusing (when focusing on an object at a distance of 1 m from the image plane).

Next, the zoom lens of Example 5 will be described. FIG. 5 is a sectional view showing the lens configuration of the zoom lens of Example 5. As shown in FIG. The group configuration of the zoom lens of Example 5 is the same as that of the zoom lens of Example 1, but during zooming, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group All lens groups of G4 are configured to move. Table 17 shows the basic lens data of the zoom lens of Example 5, Table 18 shows data on specifications, Table 19 shows data on varying surface spacing, Table 20 shows data on aspheric coefficients, and Table 20 shows data on infinite distance objects. FIG. 14 shows aberration diagrams during focusing, and FIG. 15 shows aberration diagrams during finite-distance object focusing (when focusing on an object at a distance of 1 m from the image plane).

Table 21 shows values corresponding to the conditional expressions (1) to (8) of the zoom lenses of Examples 1 to 5. Note that the d-line is used as a reference wavelength in all the examples, and the values shown in Table 21 below are for this reference wavelength.

From the above data, all the zoom lenses of Examples 1 to 5 satisfy the conditional expressions (1) to (8). It can be seen that this zoom lens provides high optical performance over the entire object distance with little fluctuation.

Next, an embodiment of an imaging device according to the present invention will be described with reference to FIGS. 16 and 17. FIG. 16 and 17 show perspective views of the front side and the back side of a camera 30. A non-removable camera 30 is detachably attached with an interchangeable lens 20 containing a zoom lens 1 according to an embodiment of the present invention in a lens barrel. It is a flex (so-called mirrorless) digital camera.

This camera 30 has a camera body 31, and a shutter button 32 and a power button 33 are provided on the upper surface thereof. Operation units 34 and 35 and a display unit 36 are provided on the rear surface of the camera body 31 . The display unit 36 is for displaying a captured image or an image within an angle of view before being captured.

A camera body 31 has a photographic opening through which light from an object to be photographed is incident at the center of the front surface of the camera body 31. A mount 37 is provided at a position corresponding to the photographic opening. 31.

In the camera body 31, there is an imaging element (not shown) such as a CCD (Charge Coupled Device) that receives a subject image formed by the interchangeable lens 20 and outputs an imaging signal corresponding to the image, and A signal processing circuit for processing an imaging signal to generate an image, a recording medium for recording the generated image, and the like are provided. With this camera 30, it is possible to take a still image or a moving image by pressing the shutter button 32, and the image data obtained by this shooting is recorded in the recording medium.

Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, the values of the curvature radius, surface spacing, refractive index, Abbe number, etc. of each lens are not limited to the values shown in the above embodiments, and may take other values.

Further, in the embodiments of the imaging device, a non-reflex type digital camera has been described with reference to the drawings, but the imaging device of the present invention is not limited to this. It is also possible to apply the present invention to imaging devices other than the flex system, such as digital cameras, movie cameras, and broadcasting cameras.

1 zoom lens 20 interchangeable lens 30 camera 31 camera body 32 shutter button 33 power button 34, 35 operation unit 36 display unit 37 mount FOCUS focusing lens group G1 first lens group G2 second lens group G3 third lens group G4 fourth Lens group L1a to L4a Lens OIS Anti-vibration lens group PP Optical member Sim Image surface St Aperture stop ta On-axis light flux at telephoto end tb Light flux at maximum angle of view at telephoto end wa On-axis light flux at wide-angle end wb Maximum angle of view at wide-angle end luminous flux Z optical axis

Claims (8)

In order from the object side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with negative refractive power, and a fourth lens with positive refractive power. consisting of groups and
During zooming, the first lens group, the second lens group, the third lens group, and the fourth lens group change distances between adjacent groups in the optical axis direction,
The third lens group is composed of a negative lens,
During focusing, only the third lens group moves along the optical axis,
The second lens group has an aperture,
The second lens group has a vibration reduction lens group that performs vibration reduction by moving in a direction perpendicular to the optical axis,
The anti-vibration lens group is arranged closer to the image side than the diaphragm,
The fourth lens group is fixed during zooming,
The fourth lens group is composed of a positive lens,
Bf is the back focus at the wide-angle end,
The maximum image height is IH ,
ft is the focal length of the entire system when focusing on an object at infinity at the telephoto end,
When fois is the focal length of the anti-vibration lens group ,
0.6<Bf/IH<1.2 (4)
0.5<ft/fois<2 (6)
A zoom lens that satisfies conditional expressions (4) and (6) expressed by: 2. The zoom lens according to claim 1 , wherein the second lens group has lenses adjacent to the object side and image side of the stop. 3. The zoom lens according to claim 2, wherein the second lens group has, in order from the object side, a positive lens and the diaphragm. 4. The zoom lens according to claim 2, wherein said second lens group has a cemented lens composed of at least one positive lens and at least one negative lens on the image side of said stop. The cemented lens consists of one positive lens and one negative lens,
When the Abbe number difference between the positive lens and the negative lens constituting the cemented lens is Δνcd,
15<Δνcd<60 (8)
5. The zoom lens according to claim 4, which satisfies conditional expression (8) represented by: 0.6<Bf/IH≦0.76 (4-3)
6. The zoom lens according to any one of claims 1 to 5 , which satisfies conditional expression (4-3) represented by: 20<Δνcd<50 (8-1)
6. The zoom lens according to claim 5 , which satisfies conditional expression (8-1) represented by: An imaging device comprising the zoom lens according to any one of claims 1 to 7 .

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