JP6944185B2 - Zoom lens system and imaging device - Google Patents

Description

The present invention relates to a zoom lens system and an imaging device including the zoom lens system.

Patent Document 1 describes, in order from the object side to the image side, a first lens group having a positive refractive force, a second lens group having a negative refractive force, a third lens group having a positive refractive force, and a third lens group having a negative refractive force. It has 4 lens groups and a 5th lens group with positive refractive power, and the distance between the 1st lens group and the 2nd lens group is large at the telescopic end compared to the wide-angle end, and the 2nd lens group and the 3rd lens group. Zooming is performed by changing the distance between adjacent lens groups so that the distance between the 3rd lens group and the 4th lens group is large and the distance between the 4th lens group and the 5th lens group is small. An optical system characterized by the above is disclosed.

Patent Document 2 describes a zoom lens composed of a first lens group, a second lens group, a third lens group, a fourth lens group, a fifth lens group, and a sixth lens group arranged in order from the object side. , The fifth lens group has a negative refractive power, and at least an optical system that changes the magnification from the wide-angle end to the telescopic end by moving the fifth lens group is disclosed.

Patent Document 3 has a plurality of lens groups composed of at least one lens element, and at least one lens group other than the lens group arranged on the most object side and the lens group arranged on the most object side. Is fixed to the image plane during zooming from the wide-angle end to the telescopic end during imaging, and at least two lens groups out of all lens groups are along the optical axis during the zooming. A zoom lens system, which is a group of moving lenses that move in a moving manner, is disclosed.

JP-A-2007-163964 Japanese Unexamined Patent Publication No. 2016-206410 International Publication WO2013 / 027364

Further, there is a demand for a lens system that is compact, lightweight, easy to handle, and capable of acquiring an image in which aberrations are well corrected, and an imaging device equipped with the lens system.

One aspect of the present invention is a zoom lens system for imaging, in which a first lens group having a negative refractive force whose position is fixed with respect to an image plane, which is arranged in order from the object side, and focusing. A second lens group that moves when zooming from the wide-angle end to the telephoto end, a third lens group that moves toward the object when zooming from the wide-angle end to the telephoto end, and an image when zooming from the wide-angle end to the telephoto end. The fourth lens group and the fifth lens group, which move to the surface side and have a negative synthetic refractive force, and the position is fixed with respect to the image surface, the aperture is arranged on the object side, and the refractive force is positive. It is composed of 6 lens groups, and the combined refractive power of the 3rd lens group and the 4th lens group is positive, the combined focal distance fGxw at the wide-angle end of those lens groups, and the focal point of the 1st lens group. The distance fG1 satisfies the following conditions.
0.75 << | fGxw / fG1 | <1.0

A zoom lens by satisfying the above conditions in combination with the first lens group having a negative refractive power, where the combined refractive power of the lens group of the combination of the third lens group and the fourth lens group is positive. It is possible to provide a lens system 10 capable of suppressing an excessively large negative power on the object side of the system, being compact, lightweight, and easy to handle, and capable of acquiring an image in which aberrations are satisfactorily corrected. More specific configurations and effects are described throughout the specification.

The total length LA of the zoom lens system and the length (total length) LG6 of the sixth lens group may satisfy the following conditions.
0.3 ≤ LG6 / LA ≤ 0.4

The third lens group may be composed of a junction lens including a lens having a negative refractive power and a lens having a positive refractive power from the object side, and a lens having a positive refractive power. Further, a zoom lens system in which the refractive index nL33 of the lens having a positive refractive power on the image plane side of the third lens group and the Abbe number νdL33 satisfy the following conditions.
1.65 <nL33 <1.90
40 <νdL33 <60

The fourth lens group may be composed of a lens having a negative refractive power from the object side and a lens having a positive refractive power, and the fifth lens group may be composed of a lens having a negative refractive power. Further, the fourth lens group has a positive or negative refractive power weaker than the refractive power of the fifth lens group, and the negative refractive power lens of the fourth lens group is a negative meniscus lens convex toward the object side. Alternatively, the negative lens having both dents and the positive refractive power lens may be a meniscus lens convex toward the object. Further, the radius of curvature RL41b of the surface of the lens having a negative refractive power on the image plane side and the radius of curvature RL42f of the surface of the lens having a positive refractive power on the object side may satisfy the following conditions.
0.8 ≦ RL41b / RL42f ≦ 1.0

Further, the lens having a negative refractive power and the lens having a positive refractive power in the fourth lens group may be joined.

The first lens group and the sixth lens group may include at least one lens having an aspherical surface on either side. The sixth lens group includes at least eight lenses, and at least eight lenses may include a plurality of lenses constituting at least two pairs of junction lenses. The sixth lens group includes a front group including six lenses arranged so as to approach or join each other on the image plane side of the diaphragm, and an imaging group arranged apart from the front group toward the image plane. The combined focal length fGF of the front group and the combined focal length fG6 of the sixth lens group, including the rear group, may satisfy the following conditions.
0.8 <fGF / fG6 <1.0

The front group of the sixth lens group includes a first biconvex lens, a first biconcave lens, a second biconvex lens, a third biconvex lens, and a second biconcave lens in order from the object side. A fourth biconvex lens may be included.

One of the other aspects of the present invention is a lens unit having the above-mentioned zoom lens system and a holder accommodating the zoom lens system.

Further, one of the other aspects of the present invention is an image pickup apparatus having the above-mentioned zoom lens system and an image pickup element arranged on the image plane side of the zoom lens system.

The figure which shows the schematic structure of the zoom lens system and the image pickup apparatus. The figure which shows the lens data. The figure which shows the aspherical coefficient. The figure which shows the numerical value which fluctuates during zooming and focusing. The figure which shows various aberrations at a wide-angle end, a telephoto end and an intermediate focal length at an infinity. The figure which shows the aberrations at the wide-angle end, the telephoto end, and the middle of which the focal length is the closest. The figure which shows the schematic structure of another example of a zoom lens system and an image pickup apparatus. The figure which shows the lens data of the system shown in FIG. The figure which shows the aspherical coefficient of the system shown in FIG. The figure which shows the numerical value which fluctuates at the time of zooming and focusing of the system shown in FIG. FIG. 7 shows various aberrations of the system shown in FIG. 7 at the wide-angle end, the telephoto end, and the middle where the focal length is infinity. FIG. 7 shows various aberrations of the system shown in FIG. 7 at the wide-angle end, the telephoto end, and the middle where the focal lengths are closest to each other.

FIG. 1 shows an example of an imaging device (camera, camera device) provided with an optical system for imaging. The camera 1 has an imaging element (imaging) arranged on an optical system (imaging optical system, imaging optical system, lens system) 10 and an image plane side (image side, imaging side, imaging side) 12 of the optical system 10. It has a device, an image plane) 5. The optical system 10 is a zoom lens system 10 for imaging, which is a lens system having 19 elements in 6 groups. Specifically, the lens system 10 moves with a first lens group G1 having a negative refractive power whose position is fixed with respect to the image plane 5, which is arranged in order from the object side 11, and which moves during focusing. The lens group G2 of 2 and the third lens group G3 having a positive refractive power that moves to the object side 11 when zooming from the wide-angle end to the telescopic end, and the image plane side when zooming from the wide-angle end to the telescopic end. The positions of the fourth lens group G4 and the fifth lens group G5, which move to 12 and have a negative synthetic refractive power, are fixed with respect to the image plane 5, and the aperture St is arranged on the object side 11, and the refractive power is Is composed of a positive sixth lens group G6.

A high-performance zoom lens system 10 having a high aberration correction ability generally has a large number of lenses and a large aperture, which makes it heavy and difficult to handle, and it is not easy to acquire a stable image. In particular, a lens system for shooting a high-quality image such as a movie has a large number of lenses, which is close to 10 to 20, and it is difficult to handle it in a handy manner. Furthermore, when the lens group moves due to zooming, the center of gravity also moves significantly. In addition, since the F value fluctuates as the aperture moves due to zooming, it requires the skill and experience of the photographer to focus and acquire an image with little fluctuation in brightness while zooming. It has become.

In this zoom lens system 10, a first lens group G1 having a negative power, a second lens group G2 having a low power for focusing adjustment, a third lens group G3 having a positive power, and a fourth lens group G3 have a positive power. It is composed of a lens group G4 and a fifth lens group G5, and is composed of a lens group Gy having a negative combined focal distance, that is, a negative power, and a sixth lens group G6 having a positive power. Therefore, the zoom lens system 10 has a negative lead negative-positive-negative-positive as an overall power configuration, and is a type in which two retrofocuses are combined. Therefore, the lens system 10 as a whole has a configuration in which a relatively large zoom ratio can be secured without increasing the lens diameter of the object side 11 so much while having a wide angle (high angle of view).

The zoom lens system 10 includes a first lens group G1 having a retrofocus configuration on the front side (object side) 11 composed of a first lens group G1 having a negative power and a third lens group G3 having a positive power. A rear side (image) composed of a lens group Gy with a negative power and a sixth lens group G6 with a positive power in a long back focus obtained by a retrofocus configuration on the front side fixed to the image plane 5. The retrofocus configuration of the surface side) 12 is incorporated, and the configuration is adopted in which the sixth lens group G6 of the image surface side 12 is fixed to the image surface 5 by aligning the aperture St. Therefore, the number of lenses included in the rear retrofocus configuration, that is, the lens group Gy and the sixth lens group G6 can be increased without increasing the total length LA of the zoom lens system, and the number of lenses is large. , The lens system 10 having a high aberration correction ability can be realized compactly.

Further, the lens system 10 includes a second lens group G2 for focusing in the front retrofocus group. Therefore, the overall configuration includes focusing lens groups (lens groups G1 and G2), variator and compensator lens groups (lens groups G3 and Gy), and most image plane side 12 relay lens groups (lens group G6). It is possible to increase the number of lenses constituting the lens group G6 on the image plane side 12 which is the relay lens group. In the wide-angle zoom lens system 10, the lens diameter of the object side 11 tends to be large, and if there are many lenses that move during zooming, the object side 11, that is, the front side has a center of gravity in the vicinity, and the center of gravity moves greatly due to zooming. Tend to do. On the other hand, in this lens system 10, the center of gravity of the lens system 10 is reduced by reducing the lens diameter on the front side by adopting the retrofocus configuration and increasing the number of lenses arranged in the lens group G6 which is a relay lens group. Can be shifted from the object side 11 which is difficult to support to the image plane side 12 which is easy to support.

In this lens system 10, with respect to the total length LA of the lens system 10 (the length from the object-side surface S1 of the lens L11 on the most object-side side to the image-plane-side surface S34 of the lens L67 on the most image-plane side). The distance Lgw (distance along the optical axis 13) at the wide-angle end from the surface S1 on the object side of the lens L11 on the most object side to the center of gravity may satisfy the following condition (0-1). Further, the difference ΔLg between the distance Lgw at the wide-angle end and the distance Lgt at the telephoto end from the object-side surface S1 of the lens L11 on the most object side and the total length LA of the lens system 10 satisfy the following condition (0-2). May be good.
0.2 <Lgw / LA <0.5 ... (0-1)
0.0001 <ΔLg / LA <0.05 ... (0-2)
The lower limit of the condition (0-1) may be 0.3, and the upper limit may be 0.4. Further, the lower limit of the condition (0-2) may be 0.0005, and the upper limit may be 0.04.

The lens groups G3 and Gy, which function as variator and compensator of the lens system 10, have a positive-negative power configuration from the object side 11. By adopting the positive-negative power configuration, when zooming from the wide-angle end to the telephoto end, the third lens group G3 moves to the object side 11, and the lens group Gy moves to the image plane side 12 as a whole. .. Therefore, it is possible to provide a lens system 10 that can suppress fluctuations in the center of gravity of the lens system 10 during zooming and is easy to handle (manipulate).

This lens system 10 fixes the first lens group G1 which has the largest effective diameter on the object side 11 and tends to be heavy, and the sixth lens group which has the largest number of lenses on the image plane side 12 and tends to be heavy. G6 is also fixed, and a second lens group G2 for focusing and a third to fifth lens group G3 to G5 for zooming are arranged between them. Since the lens group G1 on the most object side 11 and the lens group G6 on the most image plane side 12 can be fixed, the sealing property of the lens barrel or holder 15 for accommodating these lens groups can be improved, and the intrusion of dust and the like can be prevented. , A lens unit 16 having a simple structure and high strength can be provided.

Further, in the lens system 10, the positive power lens group G3 is arranged on the object side 11, and the positive power lens group G3 moves to the object side 11 when zooming from the wide-angle end to the telephoto end. In combination with the negative power lens group G1, the negative power of the object side 11 of the lens system 10 can be suppressed from becoming too large, and the lens diameter of the object side 11 can be reduced. Further, when zooming from the wide-angle end to the telephoto end, the negative power lens group Gy moves to the image plane side 12, and the distance from the aperture St is shortened to make the spread of the luminous flux input to the aperture St constant. It can be kept and the aperture St can be fixed.

When zooming from the wide-angle end to the telephoto end, the lens group Gy with an overall negative power that moves to the image plane side 12 is composed of two lens groups G4 and G5 that move independently, and the power and the amount of movement are combined. By controlling the lens, the aberration correction ability from the wide-angle end to the telephoto end can be improved, and in particular, the effect of reducing the curvature of field can be obtained.

In this example, the fourth lens group G4 has a negative power, but it may have a positive power, and the lens group G5 has a lens group G4 on the object side 11 with respect to the absolute value of the negative power. The absolute value of the power of is small, and it is a negative power as the combined power of the lens group Gy. Aberration correction is further facilitated by configuring the lens group Gy, which moves opposite to the third lens group G3 during zooming with negative power as a whole, by two independent groups G4 and G5. As described above, the fourth lens group G4 may have a positive power, but the fourth lens group G4 with a negative power has a chromatic aberration of magnification, a sagittal image plane, and a meridional image plane (tangential image plane). It is suitable for reducing the difference between the two in the entire zoom range.

The focal length fG5 of the fifth lens group G5 and the focal length fw at the wide-angle end of the zoom lens system 10 may satisfy the following condition (0-3). Correction of various aberrations can be facilitated. The lower limit may be 1.5 and the upper limit may be 1.8. Aberration correction can be performed more easily.
1.4 << | fG5 | / fw <1.9 ... (0-3)

In this lens system 10, the combined refractive power of the combined lens group Gx of the combination of the third lens group G3 and the fourth lens group G4 is positive, and as described above, in combination with the negative power lens group G1. It is possible to prevent the negative power of the object side 11 from becoming too large, and to provide a compact lens system 10. In this lens system 10, the third lens group G3 and the fourth lens group G4 come closest to the first lens group G1 at the wide-angle end where the diameter of the lens or lens group on the object side 11 is maximized. It is possible to suppress an increase in the lens diameter of the object side 11, which contributes to providing a compact and lightweight lens system 10. In this example, the third lens group G3 has a positive power and the fourth lens group G4 has a weak negative power with respect to the third lens group G3, but the fourth lens group G4 has a positive power. May be good.

Even if the combined focal length fGxw at the wide-angle end of the lens group Gx composed of the third lens group G3 and the fourth lens group G4 and the focal length fG1 of the first lens group G1 satisfy the following condition (1). good.
0.75 << | fGxw / fG1 | <1.0 ... (1)
Below the lower limit of condition (1), the ratio of the negative power of the first lens group G1 is too small, making it difficult to reduce the weight of the lens system 10, and above the upper limit, the negative power of the first lens group G1 becomes negative. The ratio of power is too large, and it becomes difficult to correct aberrations, particularly curvature of field. The lower limit of the condition (1) may be 0.8, and the upper limit may be 0.9.

Further, in this lens system 10, the diaphragm St is fixed to the image plane 5 at the time of zooming by providing the diaphragm St on the object side 11 of the lens group G6 which is a fixed relay lens group. Therefore, it is possible to provide the lens system 10 in which the F value (FNo.) Does not change during zooming. Therefore, it is possible to provide the lens system 10 which is easy to adjust the focus during zooming, has a small fluctuation in the brightness of the image, is easy to handle, and has a high aberration correction ability.

In this zoom lens system 10, the combined refractive power of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 is positive, and these lens groups G3 to G6 The combined focal length fGzw at the wide-angle end of the lens system 10 and the focal length fw of the zoom lens system 10 may satisfy the following condition (2).
1.60 ≦ fGzw / fw ≦ 2.20 ・ ・ ・ (2)
The power of the first lens group G1 is negative with respect to the rear (image plane side) 12 positive power lens group Gz, and the lower limit of the condition (2) is set as a whole in the retrofocus type zoom lens system 10. If it is lower than that, the power of the lens group Gz is too large and it is difficult to correct curvature of field at variable magnification (during zooming). On the contrary, if it exceeds the upper limit of condition (2), the power of the lens group Gz is too small. It becomes difficult to correct spherical aberration during zooming. The lower limit may be 1.70 or 1.75. The upper limit may be 2.10 or 2.05.

The configuration of the zoom lens system 10 is that the lens group (first lens group) G1 on the most object side, which is arranged in order from the object side 11 and whose position is fixed with respect to the image plane 5 and has a negative refractive force. The focus lens group (second lens group) G2 that moves during focusing and the zoom lens group (third lens group G3, 4th) that moves in opposite directions during zooming and have positive and negative refractive forces. And a lens group Gy consisting of a fifth lens group), a lens group having a positive refractive force, a lens group having a fixed position with respect to the image plane 5 and an aperture arranged on the object side 11, and a lens group having the most image plane side (the fifth lens group). 6 lens group) It is composed of G6. The first lens group G1 and the second lens group G2 are lens groups on the object side and include a focus function, and the sixth lens group G6 arranged on the image plane side 12 with the zoom lens group G3 and Gy in between is , It functions as a relay lens group that is mainly in charge of aberration correction.

By arranging the lens group G2 that moves during focusing, the lens groups G3 and Gy that move during zooming, and the fixed aperture St from the object side 11, the aperture St does not move during focus adjustment. It is possible to prevent the F value from fluctuating, further to prevent the influence on the correction of coma, and to provide the lens system 10 having good aberration correction.

It is desirable that the refractive power of the second lens group G2, which is the focus lens group, is negative, and by setting the focus group G2 to a negative power, spherical aberration can be satisfactorily corrected. Further, the combined focal length fG2 of the second lens group G2, which is the focus lens group, and the focal length fw at the wide-angle end of the zoom lens system 10 may satisfy the following condition (3).
5.0 << | fG2 / fw | <10.0 ... (3)
If it falls below the lower limit of the condition (3), the power of the focus lens group G2 becomes strong, and the fluctuation of the angle of view at the time of focusing becomes too large. If the upper limit of the condition (3) is exceeded, the power of the focus lens group G2 is too small, the amount of movement during focusing becomes large, and the lens system 10 becomes large. The lower limit of condition (3) may be 6.7.

In this lens system 10, the total length LG6 of the sixth lens group G6 (the image plane side 12 of the lens closest to the image plane side 12 from the aperture St) is arranged on the image plane side 12 most and fixed to the image plane 5. The distance to the surface of the lens system 10) is sufficient for the total length LA (distance from the surface of the lens on the most object side 11 on the object side 11 to the surface of the lens on the most image plane side 12 on the image plane side 12). It is secured for a long time so that a sufficient number of lenses required for aberration correction can be arranged. Therefore, the total length LA of the zoom lens system 10 and the length (total length) LG6 of the sixth lens group G6 may satisfy the following condition (4).
0.3 ≤ LG6 / LA ≤ 0.4 ... (4)
If it is below the lower limit of condition (4), it becomes difficult to arrange a sufficient number of lenses for aberration correction, and if it exceeds the upper limit, lenses for zooming and focusing are arranged and a space for moving is secured. It becomes difficult.

In the lens system 10, the sixth lens group G6 on the most image plane side 12, which is a relay lens group mainly for aberration correction, is arranged so as to approach or join with each other on the image plane side 12 of the aperture St. It can be composed of a front group GF composed of a plurality of lenses and a rear group GB for imaging arranged apart from the front group GF toward the image plane 5. The front group GF includes a first biconvex lens L61, a first biconcave lens L62, a second biconvex lens L63, a third biconvex lens L64, and a second biconcave lens L65 in order from the object side 11. It is composed of six lenses with a fourth biconvex lens L66. Further, the front group GF includes two sets of bonded lenses (Balsom lenses) B3 and B4 composed of at least one of the lenses included in these six lenses L61 to L66 (a set of six lenses). In this example, the first biconcave lens L62 and the second biconvex lens L63 constitute the junction lens B3, and the third biconvex lens L64 and the second biconvex lens L65 constitute the junction lens B4. There is. The bonded lens may be a lens in which three lenses are bonded (three-element balsam).

The combination of the front group GF is important for aberration correction in the meridional (tangier) plane, which is the plane including the off-axis object point and the optical axis 13. The synthetic refractive power of the front group GF and the rear group GB of the sixth lens group G6 on the image plane side 12 is positive, the synthetic focal length fGF of the front group GF and the sixth lens which is the lens group on the image plane side. The combined focal length fG6 of the group G6 may satisfy the following condition (5).
0.8 <fGF / fG6 <1.0 ... (5)
Below the lower limit of condition (5), the power of the front group GF is too strong and it becomes difficult to correct the curvature of field and chromatic aberration of magnification of the meridional (tangential), and when it exceeds the upper limit, the power of the front group GF is too weak. This makes it difficult to correct curvature of field and spherical aberration.

The rear group GB of the sixth lens group G6 is a lens group for imaging, and it is desirable to include two positive and negative lenses. Therefore, it is desirable that the sixth lens group G6 includes at least eight lenses including the front group GF and the rear group GB, and by securing the space of the condition (4), those number of lenses are arranged. can do.

FIG. 1 shows the lens arrangement in some states of the lens system 10. FIG. 1A shows a lens arrangement at the wide-angle end where the focus position is infinity, and FIG. 1B shows an intermediate lens arrangement between the wide-angle end and the telephoto end where the focus position is infinity. (C) shows the lens arrangement at the telephoto end where the focus position is infinity. Further, FIG. 1 (d) shows the lens arrangement at the telephoto end where the focus position is in the middle (1740 mm), and FIG. 1 (e) shows the lens arrangement at the telephoto end where the focus position is the shortest (short distance, 340 mm). ing.

This lens system 10 has a 6-group configuration, and the first lens group G1 having the most negative combined refractive power (power) of the object side 11 and the sixth group having the most positive combined refractive power (power) of the image plane side 12. The lens group G6 is a fixed lens group in which the distance to the image plane 5 does not change during focusing and zooming. The second lens group G2, which has a negative power and is arranged close to the image plane side 12 of the first lens group G1, does not move during zooming, and when the focus position moves from infinity to a short distance, an object It moves monotonically to the side 11.

A third lens group G3 with a positive power, a fourth lens group G4 with a negative power, and a fifth lens with a negative power, arranged between the second lens group G2 and the sixth lens group G6. Group G5 is a group of lenses for zooming that moves during zooming and does not move during focusing. The third lens group G3 moves to the object side 11 when zooming from the wide-angle end to the telephoto end, and the fourth lens group G4 and the fifth lens group G5 move to the object side 11 when zooming from the wide-angle end to the telephoto end. Move to the image plane side 12. Further, the fourth lens group G4 and the fifth lens group G5 move independently of each other. Therefore, the third, fourth, and fifth lens groups G3 to G5 form a zoom lens group that moves during zooming, and the third lens group G3 is on the object side when zooming from the wide-angle end to the telephoto end. The first sublens group of positive power, which moves to, and the fourth and fifth lens groups G4 and G5 are synthetic, which move to the image plane side when zooming from the wide-angle end to the telephoto end. A second sub-lens group and a third sub-lens group having a negative refractive power.

FIG. 2 shows the data of each lens constituting the lens system 10. The refractive index (Rdy) is the radius of curvature (mm) of each surface of each lens arranged in order from the object side 11, the interval Thi is the distance (mm) between each lens surface, and the effective diameter H * 2 is the effective of each lens surface. The diameter (diameter, mm) and refractive index nd indicate the refractive index (d line) of each lens, and the Abbe number νd indicates the Abbe number (d line) of each lens. The final distance, d35 in this example, indicates the distance (back focus, BF) between the lens system 10 and the image pickup device 5. The same applies to the following.

FIG. 3 shows the coefficients of the aspherical surface included in the lens system 10. In this example, the surface S5 of the object side 11 of the lens L13 which is the most image plane side 12 of the first lens group G1 and the image plane side 12 of the negative meniscus lens L67 belonging to the rear group GB of the sixth lens group G6. Surface S32 is an aspherical surface. Each of these lens groups G1 and G6, which are fixed and do not move during focusing and zooming, include at least one lens with at least one aspherical surface to provide full focus and zooming. Aberration correction can be performed stably and satisfactorily over the entire range of.

The aspherical surface has the coefficients K, A, B, shown in FIG. 3, where X is the coordinates in the optical axis direction, Y is the coordinates in the direction perpendicular to the optical axis, the traveling direction of the light is positive, and R is the paraxial radius of curvature. It is expressed by the following equation (X) using C, D and E. The same applies to the subsequent embodiments. In addition, "en" means "10 to the nth power".
X = (1 / R) Y ² / [1 + {1- (1 + K) (1 / R) ² Y ² } ^1/2 ]
+ AY ⁴ + BY ⁶ + CY ⁸ + DY ¹⁰ + EY ¹² ... (X)

FIG. 4 shows data at the wide-angle end, the telephoto end, and the middle of the lens system 10. FIG. 4A shows the values of the variable intervals d0, d6, d9, d14, d17 and d19 at the wide-angle end, the middle and the telephoto end when the focal length is infinity, and FIG. 4B shows the focal length. Indicates the value of each variable interval in the middle (1740 mm), and FIG. 4 (c) shows the value of each variable interval having the shortest focal length (closest contact, 340 mm). Further, FIG. 4D shows the focal length f of the lens system 10 at the wide-angle end, the intermediate and the telephoto end, and the FNo. Is shown.

5 and 6 show spherical aberration, astigmatism, and distortion of the lens system 10. The spherical aberration shows a wavelength of 435.835 nm (broken line), a wavelength of 587.560 nm (solid line), and a wavelength of 656.270 nm (dashed line). Astigmatism indicates a tangier ray T and a sagittal ray S. The same applies to the aberration diagram shown below. FIG. 5 shows the wide-angle end (FIG. 5 (a)), the middle (FIG. 5 (b)) and the telephoto end (FIG. 5 (c)) where the focal length is infinity, and FIG. 6 shows the closest focal length. The wide-angle end (FIG. 6 (a)), the middle (FIG. 6 (b)) and the telephoto end (FIG. 6 (c)) of the lens are shown.

In the lens system 10 shown in these figures, the first lens group G1 arranged on the object side 11 is a meniscus lens L11 having a positive power convex on the object side 11 arranged from the object side 11. It is composed of a meniscus lens L12 having a convex negative power on the object side 11 and a meniscus lens L13 having a convex negative power on the object side. The surface S5 of the object side 11 of the meniscus lens L13 has a small curvature (a large radius of curvature), is a substantially flat surface, and is an aspherical surface.

The second lens group G2, which is a focus lens group, is composed of a biconcave negative lens L21 and a biconvex positive lens L22 arranged in order from the object side 11, and the object is formed by these two lenses L21. A concave meniscus type junction lens B1 is configured on the side 11. A bonded lens B1 having positive and negative powers is adopted for the second lens group G2, which is a lens group for focusing, and the second lens group G2 is configured by only the bonded lens B1 as the simplest configuration. Can be done. By adopting the junction lens B1, the chromatic aberration of magnification can be reduced over the entire focus region, that is, from infinity to a short distance. In particular, by using a negative-positive combination from the object side 11, spherical aberration and axial chromatic aberration can be satisfactorily corrected.

Further, the junction lens B1 of the second lens group G2 is a combination of a lens having a negative refractive power of both concaves and a lens having a positive refractive power of both convexes, and has good spherical aberration and axial chromatic aberration. Can be corrected. The negative refractive power lens L21 and the positive refractive power lens L22 constituting the junction lens B1 may both be concave meniscus lenses on the object side 11, and this configuration also has good spherical aberration and axial chromatic aberration. However, considering the correction of spherical aberration, the combination of this example is excellent.

The third lens group G3, which is a lens group for zooming, consists of a negative meniscus lens L31 that is convex from the object side 11 to the object side 11, a biconvex positive lens L32, and a biconvex positive lens L33. The lens B2 is composed of a lens L31 having a negative refractive power and a lens L32 having a positive refractive power. The negative-positive-positive power arrangement from the object side 11 is a retrofocus type, and spherical aberration and curvature of field can be effectively corrected. Further, the spherical aberration can be corrected more satisfactorily by using the negative lens L31 as a negative meniscus lens convex on the object side 11 or a lens having both recesses close to the negative meniscus lens and arranging the biconvex lens L32 adjacent thereto.

By forming the balsam lens B2 in which they are joined, it becomes an effective configuration for correcting axial chromatic aberration and magnifying chromatic aberration. By including the junction lens B2 in the third lens group G3 that mainly functions as a variator, axial chromatic aberration can be satisfactorily corrected over the entire range of zooming from the wide-angle end to the telephoto end.

The refractive index nL33 of the lens L33 having a positive refractive power on the image plane side 12 of the third lens group G3 satisfies the following condition (6-1), and the Abbe number νdL33 satisfies the following condition (6-2). May be good.
1.65 <nL33 <1.90 ... (6-1)
40 <νdL33 <60 ... (6-2)
When the refractive index is below the lower limit of the condition (6-1), it becomes difficult to correct the spherical aberration, and when the Abbe number is less than the lower limit of the condition (6-2), it becomes difficult to correct the axial chromatic aberration. The upper limit of the condition (6-1) may be 1.80, and the lower limit of the condition (6-2) may be 50.

For the third lens group G3, a lens L33 having a high refractive index and suitable for correcting spherical aberration and curvature of field, but having a low number of abbreviations and not suitable for chromatic aberration, is used as a junction lens B2 suitable for correcting chromatic aberration. When used in combination, various aberrations including chromatic aberration, spherical aberration and curvature of field can be satisfactorily corrected over the entire range from the wide-angle end to the telescopic end.

The fourth lens group G4, which is located on the image plane side 12 of the third lens group G3 and moves to the image plane side 12 on the opposite side of the third lens group G3 when zooming from the wide-angle end to the telephoto end, It is composed of two lenses, a lens L41 having a negative refractive power and a lens L42 having a positive refractive power from the object side, and the fifth lens group G5 is composed of one lens L51 having a negative refractive power. Has been done. The fourth lens group G4 has a negative power whose absolute value is weaker than the power of the fifth lens group G5, but may have a weak positive power.

The refractive power of the fourth lens group G4 of this example is negative, and the junction lens B5 is composed of a negative lens L41 having both concaves and a positive meniscus lens L42 convex to the object side 11. The biconcave negative lens L41 is suitable for correcting coma. The meniscus lens L42 convex on the object side 11 is suitable for correcting curvature of field. Further, by using these as the junction lens B5, the difference between the sagittal image plane and the meridional image plane can be satisfactorily corrected in the entire zoom range (all zoom positions).

The negative refractive power lens L41 and the positive refractive power lens L42 may both be meniscus lenses that are convex toward the object side 11. In either case, the adjacent surfaces S16 and S17 of the adjacent lenses L41 and L42 are convex surfaces on the object side 11, and the curvature of the surface S16 on the object side 11 is large with respect to the curvature of the surface S17 (the radius of curvature is small). ) Or the same, and the Pittsburgh sum on both sides can be reduced to provide a configuration suitable for correcting curvature of field.

The radius of curvature RL41b of the surface S16 on the image plane side 12 of the lens L41 having a negative refractive power and the radius of curvature RL42f of the surface S17 on the object side 11 of the lens L42 having a positive refractive power satisfy the following condition (7). May be good.
0.8 ≦ RL41b / RL42f ≦ 1.0 ・ ・ ・ (7)
If it falls below the lower limit of the condition (7), the difference in curvature between the surfaces S16 and S17 convex on the adjacent object side 11 becomes large, and it becomes difficult to correct the curvature of field on the telephoto end side. If the upper limit of the condition (7) is exceeded, the difference in curvature between the surfaces S16 and S17 is reversed, and it becomes difficult to correct the curvature of field on the wide-angle end side. Therefore, by satisfying the condition (7), the curvature of field can be satisfactorily corrected in the entire area of zooming. The lower limit of the condition (7) may be 0.9. This case corresponds to the upper limit of condition (7).

The focal length fL41 of the negative refractive power lens L41 on the object side 11 of the fourth lens group G4 and the focal length fL42 of the positive refractive power lens L42 on the image plane side 12 satisfy the following condition (8). You may.
0.8 << | fL41 | / fL42 <1.0 ... (8)
If it falls below the lower limit of the condition (8), the power of the lens L41 having a negative refractive power is too strong, and it becomes difficult to correct astigmatism and spherical aberration. On the other hand, if the upper limit of the condition (8) is exceeded, the power of the lens L42 having a positive refractive power is too strong, and it becomes difficult to correct the chromatic aberration of magnification and the axial chromatic aberration.

Further, these lenses L41 and L42 and the focal length fw of the lens system 10 at the wide-angle end may satisfy the following conditions (9-1) and (9-2).
1.0 << | fL41 | / fw <2.0 ... (9-1)
1.0 <fL42 / fw <2.0 ... (9-2)
If it falls below the lower limit of the condition (9), the power of the respective lenses L41 and L42 is too strong, and it becomes difficult to correct the chromatic aberration of magnification, the spherical aberration, and the axial chromatic aberration. If the upper limit is exceeded, the power of the respective lenses L41 and L42 is too weak to correct axial chromatic aberration and astigmatism.

In the lens system 10 of this example, the fifth lens group G5 having a negative power has a single configuration of a negative lens L51 having both concaves, and has the simplest configuration to secure a negative power that functions as a variator. doing.

As described above, the sixth lens group G6 includes a biconvex lens L61, a biconcave lens L62, and a biconvex lens L63 arranged in order from the object side 11 on the image plane side 12 of the fixed aperture St. It is composed of eight lenses, a convex lens L64, a biconcave lens L65, a biconvex lens L66, a negative meniscus lens L67 convex on the image plane side 12, and a biconvex lens L68. The lenses L62 and L63 are joined to form a bonded lens B3, and the lenses L64 and L65 are joined to form a bonded lens B4. Further, the lens L61, the junction lens 3 and the B4, and the lens L66 are arranged near the diaphragm St at a substantially minimum interval, and form a front group GF. The negative meniscus lens L67 and the biconvex positive lens L68 are arranged apart from the front group GF on the image plane side 12 to form the rear group GB, and the lenses L67 and L68 are arranged with a substantially minimum interval. ing. As described above, the synthetic focal length fGF of the front group GF and the synthetic focal length fG6 of the sixth lens group G6 satisfy the condition (5).

The surface S32 of the image surface side 12 of the lens L67 is an aspherical surface, and the curvature of field can be satisfactorily corrected. In this lens system 10, at least one aspherical surface is arranged in each of the first lens group G1 and the sixth lens group G6 fixed with the diaphragm St interposed therebetween. As for the aspherical surface of each group, for example, the aspherical surface included in the first lens group G1 is suitable for correcting distortion, and the aspherical surface arranged in the sixth lens group G6 has curvature of field. Suitable for correction. Further, by arranging aspherical surfaces on both sides of the diaphragm St, that is, on the object side 11 and the image plane side 12, the tangential coma aberration generated before and after the diaphragm St can be satisfactorily corrected.

The numerical values of the lens system 10 and the values of each condition are as follows.
FNo. : 2.6 (fixed)
Overall length LA (mm): 225.0 (fixed)
Back focus (mm): 33.98 (fixed)
Length to the center of gravity (wide-angle end) Lgw (mm): 85.77
Length to the center of gravity (telephoto end) Lgt (mm): 93.69
Amount of movement of the center of gravity ΔLg (mm): 7.92
Overall length LG6 (mm) of the sixth lens group: 79.46
Combined focal length fw (mm) at the wide-angle end of the lens system: 40.01
Combined focal length fGxw (mm) at the wide-angle end of the third and fourth lens groups: 63.81
Combined focal length fGzw (mm) at the wide-angle end of the 3rd to 6th lens groups: 72.73
Synthetic focal length fGF (mm) in the front group of the sixth lens group: 54.59
Focal length fL41 (mm) of the negative lens L41 of the fourth lens group: -45.02
Focal length fL42 (mm) of positive lens L42 of the fourth lens group: 48.98
Condition (0-1) (Lgw / LA): 0.381
Condition (0-2) (ΔLg / LA): 0.0352
Condition (0-3) (| fG5 | / fw): 1.58
Conditions (1) (| fGxw / fG1 |): 0.866
Condition (2) (fGzw / fw): 1.818
Condition (3) (| fG2 / fw |): 7.49
Condition (4) (LG6 / LA): 0.353
Condition (5) (fGF / fG6): 0.914
Conditions (6-1) (nL33): 1.73
Condition (6-2) (νdL33): 54.7
Condition (7) (RL41b / RL42f): 1.0
Condition (8) (| fL41 | / fL42): 0.919
Condition (9-1) (| fL41 | / fw): 1.125
Condition (9-2) (fL42 / fw): 1.224

The lens system 10 shown in FIG. 1 is a compact zoom lens system that satisfies all of the conditions (0-1) to (9-2) and has a fixed length, and has a configuration of 19 elements in 6 groups. Although it is a lens system, it is a lens system that has a relatively well-balanced center of gravity on the image plane side, is in a position that is easy to hold by hand, has little movement of the center of gravity during zooming, and is easy to handle (manage). Further, in this lens system 10, FNo. Is fixed, easy to focus, clear, or desired focusing, and images with little change in brightness can be obtained. Further, as shown in FIGS. 5 and 6, it is possible to acquire an image in which various aberrations are satisfactorily corrected in the entire area of zooming and the entire area of focusing.

Further, in this lens system 10, focusing is concentrated on the second lens group G2 of the front (object side) 11 of the lens system 10, and zooming is performed on the third, fourth, and fifth lenses in the center of the lens system 10. The composition is concentrated in groups G3 to G5. Therefore, in the lens unit 16 or the image pickup apparatus 1 including the lens system 10, the focal length adjustment function (mechanism) can be concentrated in the front, and the magnification adjustment function (mechanism) is concentrated in the rear or the center. can do. Therefore, these mechanisms can be simplified, and a lightweight, high-performance and compact lens unit 16 and an imaging device 1 can be provided.

FIG. 7 shows a different example of the image pickup apparatus 1. The imaging device (camera) 1 is also arranged on the optical system (imaging optical system, imaging optical system, lens system) 10 and the image plane side (image side, imaging side, imaging side) 12 of the optical system 10. It has an image pickup element (imaging device, image plane) 5. The optical system 10 is a zoom lens system 10 for imaging, which is a lens system having 19 elements in 6 groups. The lens system 10 can be provided as a lens unit 16 housed in the holder 15 as in the above embodiment.

FIG. 7 shows the lens arrangement in some states of the lens system 10 as in FIG. 1, and FIG. 7 (a) shows the lens arrangement at the wide-angle end where the focus position is infinity, and FIG. 7 (b). ) Indicates an intermediate lens arrangement between the wide-angle end and the telephoto end where the focus position is infinity, and FIG. 7 (c) shows the lens arrangement at the telephoto end where the focus position is infinity. Further, FIG. 7 (d) shows the lens arrangement at the telephoto end where the focus position is in the middle (1740 mm), and FIG. 7 (e) shows the lens arrangement at the telephoto end where the focus position is the shortest (short distance, 340 mm). ing.

This lens system 10 also has a 6-group configuration, and the first lens group G1 having the most negative combined refractive power (power) of the object side 11 and the sixth group having the most positive combined refractive power (power) of the image plane side 12. The lens group G6 is a fixed lens group in which the distance to the image plane 5 does not change during focusing and zooming. The second lens group G2, which has a negative power and is arranged close to the image plane side 12 of the first lens group G1, does not move during zooming, and when the focus position moves from infinity to a short distance, an object It moves monotonically to the side 11.

Lens groups G3 to G5 for zooming are arranged between the second lens group G2 and the sixth lens group G6. In this example, the power of the third lens group G3 is positive and the power of the third lens group G3 is positive, and the fourth lens group. The power of G4 is positive, and the power of the fifth lens group G5 is negative. These lens groups G3 to G5 are lens groups for zooming that move during zooming and do not move during focusing. The third lens group G3 moves to the object side 11 when zooming from the wide-angle end to the telephoto end, and the fourth lens group G4 and the fifth lens group G5 move to the object side 11 when zooming from the wide-angle end to the telephoto end. Move to the image plane side 12. Further, the fourth lens group G4 and the fifth lens group G5 move independently of each other.

FIG. 8 shows the data of each lens constituting the lens system 10. FIG. 9 shows the coefficients of the aspherical surface included in the lens system 10. In this example, the surface S5 of the object side 11 of the lens L13 on the most image plane side 12 of the first lens group G1 and the object side 11 of the negative meniscus lens L67 belonging to the rear group GB of the sixth lens group G6. The surface S32 is an aspherical surface. FIG. 10 shows data at the wide-angle end, the telephoto end, and the middle of the lens system 10. FIG. 10 (a) shows the values of the variable intervals d0, d6, d9, d14, d18 and d20 at the wide-angle end, the middle and the telephoto end when the focal length is infinity, and FIG. 10 (b) shows the focal length. Indicates the value of each variable interval in the middle (1740 mm), and FIG. 10 (c) shows the value of each variable interval having the shortest focal length (closest contact, 340 mm). Further, FIG. 10D shows the focal length f of the lens system 10 at the wide-angle end, the intermediate and the telephoto end, and the FNo. Is shown.

11 and 12 show spherical aberration, astigmatism, and distortion of the lens system 10. FIG. 11 shows the wide-angle end (FIG. 11 (a)), the middle (FIG. 11 (b)) and the telephoto end (FIG. 11 (c)) where the focal length is infinity, and FIG. 12 shows the closest focal length. The wide-angle end (FIG. 12 (a)), the middle (FIG. 12 (b)) and the telephoto end (FIG. 12 (c)) of the lens are shown.

The basic configuration of the lens system 10 is the same as that of the lens system 10 shown in FIG. The first lens group G1 is a negative power lens group fixed to the object side 11 most (does not move during zooming and focusing), and the second lens group G2 focuses from infinity to the nearest lens group. It is a lens group of negative power that moves to the object side 11 at the time, and is a lens group that does not move at the time of zooming. The second lens group G2 of this example is a junction lens B1 composed of a negative meniscus lens L21 having a recess on the object side 11 and a positive meniscus lens L22 having a recess on the object side 11, which are arranged in order from the object side 11. It is composed of.

The third lens group G3 is a lens group having a positive power that moves to the object side 11 when zooming from the wide-angle end to the telephoto end, and is a lens group that does not move during focusing. The third lens group G3 of this example has a three-lens configuration consisting of a negative lens L31 having a substantially flat surface on the object side 11 and a biconvex positive lens L32, a biconvex positive lens L32, and a biconvex positive lens L33. The junction lens B2 is composed of a lens L31 having a negative refractive power and a lens L32 having a positive refractive power.

The fourth lens group G4 is a lens group having a positive power that moves to the image plane side 12 when zooming from the wide-angle end to the telephoto end, and is a lens group that does not move during focusing. The fourth lens group G4 of this example is composed of two lenses, a lens L41 having a negative refractive power and a lens L42 having a positive refractive power, both of which are meniscus lenses convex on the object side 11.

The fifth lens group G5 is a lens group having a negative power that moves to the image plane side 12 when zooming from the wide-angle end to the telephoto end, and is a lens group that does not move during focusing. The fifth lens group G5 of this example is a single lens L51 having a negative refractive power.

The sixth lens group G6 is a lens group of positive power that is arranged on the image plane side 12 most and does not move (fixed) during zooming and focusing, and is arranged in order from the object side 11 and is fixed. Aperture St, biconvex lens L61, biconcave lens L62, biconvex lens L63, biconvex lens L64, biconcave lens L65, biconvex lens L66, and negative meniscus lens L67 convex on the image plane side 12. It is composed of eight lenses with a convex lens L68. The lenses L62 and L63 are joined to form a bonded lens B3, and the lenses L64 and L65 are joined to form a bonded lens B4. Further, the lens L61, the junction lens 3 and the B4, and the lens L66 are arranged near the diaphragm St at a substantially minimum interval, and form a front group GF. The negative meniscus lens L67 and the biconvex positive lens L68 are arranged apart from the front group GF on the image plane side 12 to form the rear group GB, and the lenses L67 and L68 are arranged with a substantially minimum interval. ing. The surface S32 of the object side 11 of the lens L67 is an aspherical surface.

The numerical values of the lens system 10 and the values of each condition are as follows.
FNo. : 2.6 (fixed)
Overall length LA (mm): 225.0 (fixed)
Back focus (mm): 35.01 (fixed)
Length to the center of gravity (wide-angle end) Lgw (mm): 73.35
Length to the center of gravity (telephoto end) Lgt (mm): 73.50
Amount of movement of the center of gravity ΔLg (mm): 0.15
Overall length LG6 (mm) of the sixth lens group: 74.82
Combined focal length fw (mm) at the wide-angle end of the lens system: 40.01
Combined focal length fGxw (mm) at the wide-angle end of the 3rd and 4th lens groups: 52.86
Combined focal length fGzw (mm) at the wide-angle end of the 3rd to 6th lens groups: 78.82
Synthetic focal length fGF (mm) in the front group of the sixth lens group: 64.96
Focal length fL41 (mm) of the negative lens L41 of the fourth lens group: -68.41
Focal length fL42 (mm) of positive lens L42 of the fourth lens group: 50.18
Condition (0-1) (Lgw / LA): 0.326
Condition (0-2) (ΔLg / LA): 0.0007
Condition (0-3) (| fG5 | / fw): 1.70
Condition (1) (| fGxw / fG1 |): 0.813
Condition (2) (fGzw / fw): 1.97
Condition (3) (| fG2 / fw |): 7.55
Condition (4) (LG6 / LA): 0.333
Condition (5) (fGF / fG6): 0.963
Condition (6-1) (nL33): 1.59282
Condition (6-2) (νdL33): 68.6
Condition (7) (RL41b / RL42f): 0.953
Condition (8) (| fL41 | / fL42): 1.36
Condition (9-1) (| fL41 | / fw): 1.71
Condition (9-2) (fL42 / fw): 1.25

The lens system 10 shown in FIG. 7 satisfies the conditions (0-1) to (5), (7), (9-1), and (9-2), and is compact in length. It is a zoom lens system, which is a lens system consisting of 19 elements in 6 groups, but the center of gravity is relatively well-balanced on the image plane side, and it is in a position that is easy to hold by hand. It is a lens system that is easy to handle. Further, in this lens system 10, FNo. Is fixed, easy to focus, clear, or desired focusing, and images with little change in brightness can be obtained. Further, as shown in FIGS. 11 and 12, it is possible to acquire an image in which various aberrations are satisfactorily corrected in the entire area of zooming and the entire area of focusing.

Further, the focusing mechanism and the zooming mechanism can be centrally arranged in the front and the rear, respectively, in common with the lens system 10 of the above-described embodiment, which is a lightweight, high-performance and compact lens unit 16 and an imaging device. 1 can be provided.

1 Imaging device (camera), 10 Lens system 15 Holder (lens barrel), 16 Lens unit

Claims (14)

A zoom lens system for imaging
A first lens group with a negative refractive power whose position is fixed with respect to the image plane, arranged in order from the object side,
A second lens group that moves only during focusing,
A third lens group with positive refractive power that moves toward the object when zooming from the wide-angle end to the telephoto end,
A fourth lens group and a fifth lens group having a negative synthetic refractive power that move toward the image plane when zooming from the wide-angle end to the telephoto end,
The position is fixed with respect to the image plane, the diaphragm is arranged on the object side, and it is composed of a sixth lens group having a positive refractive power.
The combined refractive power of the third lens group and the fourth lens group is positive, and the combined focal length fGxw at the wide-angle end of those lens groups and the focal length fG1 of the first lens group are as follows. A zoom lens system that meets the conditions.
0.75 << | fGxw / fG1 | <1.0 In claim 1,
A zoom lens system in which the total length LA of the zoom lens system and the length LG6 of the sixth lens group satisfy the following conditions.
0.3 ≤ LG6 / LA ≤ 0.4 In claim 1 or 2,
The third lens group is a zoom lens system composed of a junction lens composed of a lens having a negative refractive power and a lens having a positive refractive power from the object side, and a lens having a positive refractive power. In claim 3,
A zoom lens system in which the refractive index nL33 of the lens having a positive refractive power on the image plane side of the third lens group and the Abbe number νdL33 satisfy the following conditions.
1.65 <nL33 <1.90
40 <νdL33 <60 In any of claims 1 to 4,
The fourth lens group is composed of a lens having a negative refractive power from the object side and a lens having a positive refractive power.
The fifth lens group is a zoom lens system composed of lenses having a negative refractive power. In claim 5,
The fourth lens group has an absolute positive or negative refractive power smaller than the absolute value of the negative refractive power of the fifth lens group, and the negative refractive power lens of the fourth lens group. Is a negative meniscus lens that is convex to the object side or a negative lens that is both concave, and the lens having a positive refractive power is a meniscus lens that is convex to the object side, a zoom lens system. In claim 6,
A zoom lens system in which the radius of curvature RL41b of the surface of the lens having a negative refractive power on the image plane side and the radius of curvature RL42f of the surface of the lens having a positive refractive power on the object side satisfy the following conditions.
0.8 ≦ RL41b / RL42f ≦ 1.0 In claim 6 or 7,
A zoom lens system in which the negative refractive power lens and the positive refractive power lens of the fourth lens group in the previous term are joined. The zoom lens system according to any one of claims 1 to 8, wherein the first lens group and the sixth lens group include at least one lens having an aspherical surface on either side. In any of claims 1 to 9,
A zoom lens system in which the sixth lens group comprises at least eight lenses, the at least eight lenses comprising a plurality of lenses constituting at least two pairs of junction lenses. In any of claims 1 to 10,
The sixth lens group was arranged on the image plane side of the diaphragm with a front group including six lenses arranged so as to approach or join with each other and a front group separated from the front group toward the image plane. A zoom lens system including a rear group for imaging, in which the synthetic focal length fGF of the front group and the synthetic focal length fG6 of the sixth lens group satisfy the following conditions.
0.8 <fGF / fG6 <1.0 In claim 11, the front group includes a first biconvex lens, a first biconcave lens, a second biconvex lens, a third biconvex lens, and a second biconcave lens in order from the object side. A zoom lens system that includes a fourth biconvex lens. The zoom lens system according to any one of claims 1 to 12.
A lens unit having a holder that houses the zoom lens system. The zoom lens system according to any one of claims 1 to 12.
An image pickup device having an image pickup element arranged on the image plane side of the zoom lens system.

Images