JP2011248269A - Zoom lens system, imaging device and camera system - Google Patents

Abstract

A zoom lens system having high resolution, a short optical total length, a large zoom ratio of about 5 times, and an angle of view at a wide angle end of about 85 °, which can be sufficiently adapted to wide angle photography. .
In order from an object side to an image side, a first lens group having negative power and having two lens elements, a second lens group having positive power, and at least one refractive power are provided. And a subsequent group, and during zooming from the wide-angle end to the telephoto end during imaging, each lens group is moved along the optical axis to perform zooming, and the first lens group has negative power Consists of a biconcave lens element and a meniscus lens element having positive power and a convex surface facing the object side, and an aperture that moves on the optical axis together with the second lens group during zooming The stop is disposed on the image plane side of the second lens group, and satisfies the condition 3.5 <fT / fW <10 (fW: focal length of the entire system at the wide angle end, fT: focal length of the entire system at the telephoto end). Zoom lens system.
[Selection] Figure 1

Description

  The present invention relates to a zoom lens system. In particular, the present invention not only has a high resolution, but also has a short optical total length (lens total length: the distance from the apex of the lens surface closest to the object side to the image plane in the entire lens system) and a variable magnification ratio. The present invention relates to a zoom lens system that is as large as about 5 times and has a field angle of about 85 ° at the wide-angle end and can be sufficiently adapted to wide-angle shooting.

  In recent years, solid-state imaging devices such as high-pixel CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor) have been developed, and an imaging optical system having high optical performance corresponding to these high-pixel solid-state imaging devices has been developed. Digital still cameras and digital video cameras (hereinafter simply referred to as “digital cameras”) equipped with an imaging device are rapidly spreading. Among digital cameras having such high optical performance, the demand for particularly compact type digital cameras is increasing.

  The compact digital camera is required to be thinner because it is easy to carry and store. In order to realize such a compact and thin digital camera, conventionally, in order from the object side to the image side, a first lens group having a negative power, a second lens group having a positive power, and a power Various zoom lens systems having a short optical total length have been proposed with a negative lead type zoom configuration in which at least one succeeding group having a zoom lens is disposed.

  Patent Document 1 has three negative and positive lens groups in order from the object side to the image side, the distance between the lens groups changes at the time of zooming, and the aperture is between the first lens group and the second lens group. And a zoom lens system in which the second lens group is composed of three lenses.

  Patent Document 2 has at least two negative and positive lens groups in order from the object side to the image side, and the distance between the lens groups changes at the time of zooming, and the refractive index and focus of the lens constituting the first lens group. A zoom lens in which the distance and the radius of curvature satisfy a specific relationship is disclosed.

  Patent Document 3 discloses a zoom lens system that includes three negative and positive lens groups in order from the object side to the image side, and the first group closest to the object side is a cemented lens.

  Patent Document 4 has at least three lens groups of negative positive and negative or positive in order from the object side to the image side, and the first group closest to the object side includes at least one positive lens and at least one lens. A zoom lens system including a negative lens plastic lens is disclosed.

JP 2010-61007 A JP 2007-140359 A JP 2009-47986 A International Publication No. 2008/0775566

  However, although the zoom lens system disclosed in Patent Document 1 has a zoom ratio of about 5 times, the lens configuration of the second lens group is one positive lens and one set in order from the object side to the image side. Since the lens is composed of a small number of lenses, it is difficult to sufficiently correct aberrations.

  In addition, the zoom lens system disclosed in Patent Document 2 has a short optical total length and can further reduce the thickness of the camera. However, the zoom ratio is as small as about 3 times, and the angle of view at the wide angle end is as small as 56 °. The demand for a compact type digital camera whose zoom ratio has been increasing in recent years cannot be satisfied.

  The zoom lens system disclosed in Patent Document 3 also has a short optical total length because the first lens group is made of a cemented lens, and the camera can be made thinner, but the zoom ratio is as small as about three times. The demand for a compact digital camera with a large zoom ratio cannot be satisfied.

  The zoom lens system disclosed in Patent Document 4 also has a short optical total length and can further reduce the thickness of the camera. However, the zoom ratio is as small as about three times, and a compact type digital camera that has recently increased in magnification ratio. It cannot satisfy the demand for cameras.

  An object of the present invention is to provide a high-performance zoom lens system having a well-balanced balance between a wide angle of view at the wide-angle end and a high zooming ratio, while the lens overall length is very short and compact, and an imaging apparatus including the zoom lens system. And a thin and compact camera equipped with the imaging device.

  One of the above objects is achieved by the following zoom lens system. That is, the present invention is a zoom lens system having a plurality of lens groups each composed of at least one lens element, and has negative power in order from the object side to the image side, and is composed of two lens elements. A first lens group; a second lens group having a positive power; and a succeeding group having at least one refractive power; the first lens group during zooming from the wide-angle end to the telephoto end during imaging Each lens group is moved along the optical axis so as to reduce the distance between the first lens group and the second lens group, and zooming is performed. The first lens group is a biconcave having negative power in order from the object side. An aperture stop having a positive lens shape and a meniscus lens element having a positive power and having a convex surface facing the object side, and moves on the optical axis together with the second lens group during zooming On the image plane side of the second lens group Arranged, the zoom lens system satisfies the following condition (1).

3.5 <fT / fW <10 (1)
About.
here,
fW: focal length of the entire system at the wide-angle end fT: focal length of the entire system at the telephoto end,
It is.

  One of the above objects is achieved by the following zoom lens system. That is, the present invention is a zoom lens system having a plurality of lens groups each composed of at least one lens element, and has negative power in order from the object side to the image side, and is composed of two lens elements. A first lens group; a second lens group having a positive power; and a succeeding group having at least one refractive power; the first lens group during zooming from the wide-angle end to the telephoto end during imaging Each lens group is moved along the optical axis so as to reduce the distance between the first lens group and the second lens group, and zooming is performed. The first lens group is a biconcave having negative power in order from the object side. An aperture stop having a positive lens shape and a meniscus lens element having a positive power and having a convex surface facing the object side, and moves on the optical axis together with the second lens group during zooming On the image plane side of the second lens group Placed, the imaging apparatus including the zoom lens system satisfies the following condition (1).

3.5 <fT / fW <10 (1)
About.
here,
fW: focal length of the entire system at the wide-angle end fT: focal length of the entire system at the telephoto end,
It is.

  One of the above objects is achieved by the following zoom lens system. That is, the present invention is a zoom lens system having a plurality of lens groups each composed of at least one lens element, and has negative power in order from the object side to the image side, and is composed of two lens elements. A first lens group; a second lens group having a positive power; and a succeeding group having at least one refractive power; the first lens group during zooming from the wide-angle end to the telephoto end during imaging Each lens group is moved along the optical axis so as to reduce the distance between the first lens group and the second lens group, and zooming is performed. The first lens group is a biconcave having negative power in order from the object side. An aperture stop having a positive lens shape and a meniscus lens element having a positive power and having a convex surface facing the object side, and moves on the optical axis together with the second lens group during zooming On the image plane side of the second lens group Placed, a camera system including the zoom lens system satisfies the following condition (1).

3.5 <fT / fW <10 (1)
About.
here,
fW: focal length of the entire system at the wide-angle end fT: focal length of the entire system at the telephoto end,
It is.

  According to the present invention, not only has the high resolution, but also the optical total length is short, the zoom ratio is as large as about 5 times, and the angle of view at the wide angle end is about 85 °, which is sufficient for wide angle photography. It is possible to provide a zoom lens system that can be adapted to the above.

Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 1 (Example 1) Longitudinal aberration diagram of the zoom lens system according to Example 1 in an infinitely focused state Lateral aberration diagram in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Embodiment 1 Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 2 (Example 2) Longitudinal aberration diagram of the zoom lens system according to Example 2 in an infinitely focused state Lateral aberration diagrams in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Example 2 Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 3 (Example 3) Longitudinal aberration diagram of the zoom lens system according to Example 3 in an infinitely focused state Lateral aberration diagram in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Example 3 Lens arrangement diagram showing an infinitely focused state of the zoom lens system according to Embodiment 4 (Example 4) Longitudinal aberration diagram of the zoom lens system according to Example 4 in an infinitely focused state Lateral aberration diagrams in the basic state where image blur correction is not performed and in the image blur correction state at the telephoto end of the zoom lens system according to Example 4 Schematic configuration diagram of a digital still camera according to Embodiment 1

(Embodiments 1 to 4)
1, 4, 7, and 10 are lens arrangement diagrams of the zoom lens systems according to Embodiments 1, 2, 3, and 4, respectively, and each represents a zoom lens system in an infinitely focused state.

  In each figure, (a) shows a lens configuration at the wide angle end (shortest focal length state: focal length fw), and (b) shows an intermediate position (intermediate focal length state: focal length fM = √ (fW * fT)). Lens configuration, (c) shows the lens configuration at the telephoto end (longest focal length state: focal length fT). Also, in each figure, the broken line arrows provided between FIGS. (A) and (b) are obtained by connecting the positions of the lens groups in the wide-angle end, the intermediate position, and the telephoto end in order from the top. Straight line. Therefore, between the wide-angle end and the intermediate position, and between the intermediate position and the telephoto end are simply connected by a straight line, which is different from the actual movement of each lens group. Furthermore, in each figure, the arrow attached to the lens group represents the focusing from the infinite focus state to the close object focus state. That is, the moving direction during focusing from the infinitely focused state to the close object focused state is shown.

  In FIGS. 1, 4, 7, and 10, an asterisk * attached to a specific surface indicates that the surface is an aspherical surface. In each figure, a symbol (+) and a symbol (−) attached to a symbol of each lens group correspond to a power symbol of each lens group. In each figure, the straight line described on the rightmost side represents the position of the image plane S, and is located on the object side of the image plane S (between the image plane S and the most image side lens surface of the third lens group G3). Are provided with a parallel flat plate equivalent to an optical low-pass filter, a face plate of an image sensor, or the like.

  Further, in FIGS. 1, 4, 7, and 10, an aperture stop A is provided between the second lens group G2 and the third lens group G3. The aperture stop A moves on the optical axis integrally with the second lens group G2 during zooming from the wide-angle end to the telephoto end during photographing.

  As shown in FIG. 1, in the zoom lens system according to Embodiment 1, the first lens group G1 includes, in order from the object side to the image side, a biconcave first lens element L1 having negative power, It has a positive meniscus second lens element L2 having positive power and having a convex surface facing the object side. The first lens element L1 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 1, the second lens group G2 includes, in order from the object side to the image side, a positive meniscus third lens element L3 with a convex surface facing the object side, and a convex surface facing the object side. The fourth lens element L4 having a positive meniscus shape, the fifth lens element L5 having a negative meniscus shape having a convex surface facing the object side, and the sixth lens element L6 having a biconvex shape. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented. The third lens element L3 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 1, the third lens unit G3 comprises solely a bi-convex seventh lens element L7. The seventh lens element L7 has two aspheric surfaces. The seventh lens element L7 is made of a resin material.

  In the zoom lens system according to Embodiment 1, a parallel plate L8 is provided on the object side of the image plane S (between the image plane S and the seventh lens element L7).

  In the zoom lens system according to Embodiment 1, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 moves toward the object side along a locus convex to the image side, and the second lens The group G2 moves monotonously to the object side, and the third lens group G3 moves monotonously to the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the image plane S Each lens group moves along the optical axis so that the interval between and increases monotonously.

  Further, at the time of focusing from the infinite focus state to the close junction focus state, the third lens group G3 moves toward the object side along the optical axis.

  As shown in FIG. 4, in the zoom lens system according to Embodiment 2, the first lens group G1 includes a biconcave first lens element L1 having negative power in order from the object side to the image side. And a positive meniscus second lens element L2 having positive power and having a convex surface facing the object side. The first lens element L1 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 2, the second lens group G2 includes, in order from the object side to the image side, a positive meniscus third lens element L3 with a convex surface facing the object side, and a convex surface facing the object side. The fourth lens element L4 having a positive meniscus shape, the fifth lens element L5 having a negative meniscus shape having a convex surface facing the object side, and the sixth lens element L6 having a biconvex shape. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented. The third lens element L3 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 2, the third lens unit G3 comprises solely a bi-convex seventh lens element L7. The seventh lens element L7 has two aspheric surfaces. The seventh lens element L7 is made of a resin material.

  In the zoom lens system according to Embodiment 2, a parallel plate L8 is provided on the object side of the image plane S (between the image plane S and the seventh lens element L7).

  In the zoom lens system according to Embodiment 2, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 moves toward the object side along a locus convex to the image side, and the second lens The group G2 moves monotonously to the object side, and the third lens group G3 moves monotonously to the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the image plane S Each lens group moves along the optical axis so that the interval between and increases monotonously.

  Further, at the time of focusing from the infinite focus state to the close junction focus state, the third lens group G3 moves toward the object side along the optical axis.

  As shown in FIG. 7, in the zoom lens system according to Embodiment 3, the first lens group G1 includes, in order from the object side to the image side, a biconcave first lens element L1 having negative power, It has a positive meniscus second lens element L2 having positive power and having a convex surface facing the object side. The first lens element L1 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 3, the second lens group G2 includes, in order from the object side to the image side, a positive meniscus third lens element L3 with a convex surface facing the object side, and a convex surface facing the object side. The fourth lens element L4 having a positive meniscus shape, the fifth lens element L5 having a negative meniscus shape having a convex surface facing the object side, and the sixth lens element L6 having a biconvex shape. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented. The third lens element L3 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 3, the third lens unit G3 comprises solely a bi-convex seventh lens element L7. The seventh lens element L7 has two aspheric surfaces. The seventh lens element L7 is made of a resin material.

  In the zoom lens system according to Embodiment 3, a parallel plate L8 is provided on the object side of the image plane S (between the image plane S and the seventh lens element L7).

  In the zoom lens system according to Embodiment 3, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 moves toward the object side along a locus convex to the image side, and the second lens The group G2 monotonously moves toward the object side, and the third lens group G3 moves toward the image side while drawing a convex locus on the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the image plane S Each lens group moves along the optical axis so that the distance between and the lens draws a convex locus on the object side.

  Further, at the time of focusing from the infinite focus state to the close junction focus state, the third lens group G3 moves toward the object side along the optical axis.

  As shown in FIG. 10, in the zoom lens system according to Embodiment 4, the first lens group G1 includes, in order from the object side to the image side, a biconcave first lens element L1 having negative power, It has a positive meniscus second lens element L2 having positive power and having a convex surface facing the object side. The first lens element L1 has two aspheric surfaces.

  In the zoom lens system according to Embodiment 4, the second lens unit G2 includes, in order from the object side to the image side, a positive meniscus third lens element L3 with a convex surface facing the object side, and a convex surface facing the object side. The fourth lens element L4 having a positive meniscus shape, the fifth lens element L5 having a negative meniscus shape having a convex surface facing the object side, and the sixth lens element L6 having a biconvex shape. Among these, the fourth lens element L4 and the fifth lens element L5 are cemented. The third lens element L3 has an aspheric object side surface.

  In the zoom lens system according to Embodiment 4, the third lens unit G3 comprises solely a bi-convex seventh lens element L7. The seventh lens element L7 has two aspheric surfaces. The seventh lens element L7 is made of a resin material.

  In the zoom lens system according to Embodiment 4, a parallel plate L8 is provided on the object side of the image plane S (between the image plane S and the seventh lens element L7).

  In the zoom lens system according to Embodiment 4, during zooming from the wide-angle end to the telephoto end during imaging, the first lens group G1 moves toward the object side along a locus convex to the image side, and the second lens The group G2 monotonously moves toward the object side, and the third lens group G3 moves toward the image side while drawing a convex locus on the object side. That is, during zooming, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the image plane S Each lens group moves along the optical axis so that the interval between and decreases monotonously.

  Further, at the time of focusing from the infinite focus state to the close junction focus state, the third lens group G3 moves toward the object side along the optical axis.

  In the zoom lens systems according to Embodiments 1 to 4, the first lens group G1 has positive power with a distance from the lens element having negative power in order from the object side to the image side. Because it is composed of a meniscus lens element with a convex surface facing the object side, it is possible to realize a short optical total length while satisfactorily correcting various aberrations, particularly distortion and field curvature at the wide-angle end. Can do.

  In the zoom lens systems according to Embodiments 1 to 4, since the first lens group G1 is composed of a biconcave lens element having negative power on the object side, the radius of curvature on the image plane side is relatively large. Since it can be increased, the curvature of field at the wide-angle end can be corrected particularly well.

  In the zoom lens systems according to Embodiments 1 to 4, since the first lens group G1 includes at least one lens element having an aspherical surface, aberration can be corrected more satisfactorily in the entire zoom range.

  In the zoom lens systems according to Embodiments 1 to 4, since the biconcave lens element in the first lens group includes at least one aspheric surface, the field curvature at the wide-angle end is further improved. It can be corrected.

  In the zoom lens systems according to Embodiments 1 to 4, since the third lens group G3 is composed of one lens element, the total number of lens elements is reduced and the lens system has a short optical total length. . In addition, since one lens element constituting the third lens group G3 includes an aspherical surface, aberration can be corrected more satisfactorily.

  In the zoom lens systems according to Embodiments 1 to 4, since the second lens group G2 includes four lens elements including a pair of cemented lens elements therein, the spherical aberration is favorably corrected. be able to.

  In the zoom lens systems according to Embodiments 1 to 4, the first lens group G1, the second lens group G2, and the third lens group G3 are used as optical axes during zooming from the wide-angle end to the telephoto end during imaging. Each of the first lens group G1, the second lens group G2, and the third lens group G3, or some sub-lens groups of each lens group is used for zooming. Is moved in a direction perpendicular to the optical axis, image point movement due to vibration of the entire system can be corrected, that is, image blur due to camera shake, vibration or the like can be optically corrected.

  When correcting the image point movement due to the vibration of the entire system, for example, by moving the second lens group G2 in a direction perpendicular to the optical axis, while suppressing the increase in size of the entire zoom lens system, Image blur can be corrected while maintaining excellent imaging characteristics with small decentration coma and decentering astigmatism.

  In addition, when one lens group is composed of a plurality of lens elements, a part of the sub-lens groups of each lens group is any one of the plurality of lens elements or adjacent to each other. A plurality of lens elements.

  The following description is given for conditions preferred to be satisfied by a zoom lens system like the zoom lens systems according to Embodiments 1 to 4. A plurality of preferable conditions are defined for the zoom lens system according to each embodiment, but a zoom lens system configuration that satisfies all of the plurality of conditions is most desirable. However, by satisfying individual conditions, it is possible to obtain a zoom lens system that exhibits the corresponding effects.

  It is desirable that the zoom lens system according to each embodiment satisfies the following conditions.

  A zoom lens system having a plurality of lens groups each composed of at least one lens element, and having a negative power in order from the object side to the image side in sequence, a first lens group consisting of two lens elements And a second lens group having a positive power and a succeeding group having at least one refractive power, and when zooming from the wide-angle end to the telephoto end during imaging, the first lens group and the second lens A zoom lens system that performs zooming by moving each lens group along an optical axis so that a distance from the group decreases, and the first lens group has negative power in order from the object side. Consisting of a biconcave lens element and a meniscus lens element with positive power and a convex surface facing the object side, it provides excellent field curvature at the wide-angle end and spherical aberration at the telephoto end. It can be corrected.

  Further, an aperture stop that moves integrally with the second lens unit during zooming on the optical axis is arranged on the image plane side of the second lens unit, so that the first lens unit and the second lens unit at the telephoto end. The zoom lens system can be miniaturized.

  It is desirable that the zoom lens system according to each embodiment satisfies the following condition (1).

3.5 <fT / fW <10 (1)
here,
fW: focal length of the entire system at the wide-angle end fT: focal length of the entire system at the telephoto end,
It is.

  The condition (1) is a condition that defines the zoom ratio. If the upper limit of condition (1) is exceeded, the total optical length at the telephoto end becomes long, and it becomes difficult to reduce the size of the zoom lens. Further, if the lower limit of the condition (1) is not reached, the demand for a compact type digital camera whose zoom ratio has been increasing in recent years cannot be satisfied.

  It should be noted that the above effect can be further achieved by further satisfying the following condition (1) ′.

4 <fT / fW <8 (1) ′
In addition, it is desirable that the zoom lens system according to each embodiment satisfies the following condition (2).

0.3 <SF_L1 <1.0 (2)
(However, ωW> 35 °)
here,
SF_L1 = (R1 + R2) / (R1-R2)
R1: radius of curvature of the object side surface of the lens element having negative power arranged in the first lens group R2: radius of curvature of the image side surface of the lens element having negative power arranged in the first lens group ωW: Half value of maximum field angle at wide-angle end (°)
It is.

  The condition (2) is a condition for defining the shape factor of the lens element having negative power arranged in the first lens group. If the upper limit of condition (1) is exceeded, the lens element has a meniscus shape, the radius of curvature in the vicinity of the optical axis on the side surface of the image decreases, and the field curvature at the wide-angle end and spherical aberration at the telephoto end greatly fall to the image side. Aberration correction becomes difficult. On the other hand, if the lower limit of condition (1) is not reached, the radius of curvature near the optical axis on the side surface of the image becomes too large, the curvature of field at the wide-angle end and the spherical aberration at the telephoto end are greatly tilted toward the object side, thereby correcting aberrations. It becomes difficult. Aberration correction is difficult because, in a zoom lens system with a wide angle of view at the wide-angle end, the variation in aberrations of field curvature on the wide-angle side becomes large, and in order to improve performance in the entire zoom range. Satisfies the condition (2).

  It should be noted that the above effect can be further achieved by further satisfying the following condition (2) ′.

0. 5 <SF_L1 <1.0 (2) ′
(However, ωW> 35 °)
In addition, since the first lens group includes at least one lens element having an aspherical surface, aberration can be corrected more satisfactorily in the entire zoom range.

  In particular, the curvature of field at the wide-angle end can be improved by making at least one surface of the biconcave lens element in the first lens group an aspherical surface.

  In the zoom lens system according to each embodiment, the zoom lens system can be reduced in size by suppressing the thickness of the zoom group by configuring the second lens group with four lenses, and further, from the wide-angle end to the telephoto end. Aberration correction over the entire zoom range is easy, and sufficient performance can be ensured even when the F-number is as bright as 1.6 to 2.8 at the wide-angle end.

  In the zoom lens system according to each embodiment, the lens surface closest to the image side of the second lens group has a convex shape on the image plane side, and is thus arranged on the image plane side of the second lens group. Even if the distance between the aperture stop and the lens surface on the optical axis is made closer, it is easy to ensure the distance between the lens surface end and the stop member, so that the optical system can be downsized.

  In addition, it is desirable that the zoom lens system according to each embodiment satisfies the following condition (3).

0.00 <ts / fw <1.00 (3)
here,
ts: Distance between the lens surface closest to the image plane in the second lens group and the aperture stop The condition (3) defines the distance between the lens surface closest to the image plane in the second lens group and the aperture stop. It is a condition for. If the upper limit of condition (3) is exceeded, the distance between the second lens group and the aperture stop becomes too large, and the zoom lens system becomes large. On the other hand, if the lower limit of the condition (3) is not reached, the end of the lens surface and the diaphragm member are too close to each other, making it difficult to arrange the diaphragm member.

  It should be noted that the above effect can be further achieved by further satisfying the following condition (3) ′.

0.02 <ts / fw <0.4 (3) ′
Furthermore, in the zoom lens system according to each embodiment, the second lens group may be configured with one set of cemented lenses or two sets of cemented lenses.

  In the zoom lens system according to each embodiment, the third lens group is made of resin, but a non-resin material may be used.

  Each lens group of the zoom lens system according to each embodiment includes a refractive lens element that deflects incident light by refraction (that is, a lens element that deflects at an interface between media having different refractive indexes). However, the present invention is not limited to this. For example, a diffractive lens element that deflects incident light by diffraction, a refractive / diffractive hybrid lens element that deflects incident light by a combination of diffractive action and refractive action, and a refractive index that deflects incident light according to the refractive index distribution in the medium Each lens group may be composed of a distributed lens element or the like.

  Further, in each embodiment, an optical low-pass filter, a face plate of an image sensor, or the like is equivalent to the object side of the image plane S (between the image plane S and the most image side lens surface of the third lens group G3). Although a configuration in which parallel plates are arranged is shown, as this low-pass filter, a birefringent low-pass filter made of quartz or the like whose predetermined crystal axis direction is adjusted, and required optical cutoff frequency characteristics A phase type low-pass filter or the like that achieves the above by the diffraction effect is applicable.

(Embodiment 5)
FIG. 13 is a schematic configuration diagram of a digital still camera according to the fifth embodiment. In FIG. 13, the digital still camera includes an image pickup apparatus including a zoom lens system 1 and an image pickup device 2 that is a CCD, a liquid crystal monitor 3, and a housing 4. As the zoom lens system 1, the zoom lens system according to Embodiment 1 is used. In FIG. 13, the zoom lens system 1 includes a first lens group G1, a second lens group G2, an aperture stop A, and a third lens group G3 in order from the object side to the image side. In the housing 4, the zoom lens system 1 is disposed on the front side, and the imaging element 2 is disposed on the rear side of the zoom lens system 1. A liquid crystal monitor 3 is disposed on the rear side of the housing 4, and an optical image of the subject by the zoom lens system 1 is formed on the image plane S.

  The lens barrel includes a main lens barrel 5, a movable lens barrel 6, and a cylindrical cam 7. When the cylindrical cam 7 is rotated, the first lens group G1, the second lens group G2, the aperture stop A, and the third lens group G3 move to predetermined positions with reference to the image sensor 2, and from the wide-angle end to the telephoto end. Zooming can be performed. The third lens group G3 is movable in the optical axis direction by a focus adjustment motor.

  Thus, by using the zoom lens system according to Embodiment 1 for a digital still camera, it is possible to provide a small digital still camera that has a high ability to correct resolution and curvature of field and has a short optical total length when not in use. it can. In the digital still camera shown in FIG. 13, any of the zoom lens systems according to Embodiments 2 to 4 may be used instead of the zoom lens system according to Embodiment 1. The optical system of the digital still camera shown in FIG. 13 can also be used for a digital video camera for moving images. In this case, not only a still image but also a moving image with high resolution can be taken.

  In the digital still camera according to the fifth embodiment, the zoom lens system according to the first embodiment is shown as the zoom lens system 1. However, these zoom lens systems do not have to use the entire zooming area. . That is, a range in which the optical performance is ensured may be cut out according to a desired zooming area, and used as a zoom lens system having a lower magnification than the zoom lens system described in the first to fourth embodiments.

  Furthermore, although Embodiment 5 showed the example which applied the zoom lens system to the lens barrel of what is called a retractable structure, it is not restricted to this. For example, a prism having an internal reflection surface or a surface reflection mirror may be disposed at an arbitrary position such as in the first lens group G1, and the zoom lens system may be applied to a so-called bent lens barrel. Further, in the fifth embodiment, some lens groups constituting the zoom lens system such as the entire second lens group G2, the entire third lens group G3, and a part of the second lens group G2 are irradiated with light when retracted. The zoom lens system may be applied to a so-called sliding lens barrel that is retracted from the axis.

  In the digital still camera according to the fifth embodiment, the zoom lens system according to the first to fourth embodiments is used. However, the present invention is not limited to this. For example, image blur correction may be performed by vibrating the image sensor 2 in the direction perpendicular to the optical axis during camera shake.

  In addition, an imaging apparatus including the zoom lens system according to Embodiments 1 to 4 described above and an imaging element such as a CCD or a CMOS is used as a monitoring camera in a mobile phone device, a PDA (Personal Digital Assistance), or a monitoring system. The present invention can also be applied to imaging devices such as Web cameras and in-vehicle cameras, and camera systems including these cameras.

  Hereinafter, numerical examples in which the zoom lens systems according to Embodiments 1 to 4 are specifically implemented will be described. In each numerical example, the unit of length in the table is “mm”, and the unit of angle of view is “°”. In each numerical example, r is a radius of curvature, d is a surface interval, nd is a refractive index with respect to the d line, and vd is an Abbe number with respect to the d line. In each numerical example, the surface marked with * is an aspherical surface, and the aspherical shape is defined by the following equation.

Here, κ is a conic constant, and A4, A6, A8, A10, A12, A14, and A16 are fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, and sixteenth-order aspheric coefficients, respectively. .

  2, 5, 8, and 11 are longitudinal aberration diagrams of the zoom lens systems according to Embodiments 1, 2, 3, and 4, respectively.

  In each longitudinal aberration diagram, (a) shows the aberration at the wide angle end, (b) shows the intermediate position, and (c) shows the aberration at the telephoto end. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left side. In the spherical aberration diagram, the vertical axis represents the F number (indicated by F in the figure), the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line (C- line). In the astigmatism diagram, the vertical axis represents the image height (indicated by H in the figure), the solid line represents the sagittal plane (indicated by s), and the broken line represents the meridional plane (indicated by m in the figure). is there. In the distortion diagram, the vertical axis represents the image height (indicated by H in the figure).

  3, 6, 9, and 12 are lateral aberration diagrams at the telephoto end of the zoom lens systems according to Embodiments 1, 2, 3, and 4, respectively.

  In each lateral aberration diagram, the upper three aberration diagrams show a basic state in which image blur correction is not performed at the telephoto end, and the lower three aberration diagrams move the entire second lens group G2 by a predetermined amount in a direction perpendicular to the optical axis. This corresponds to the image blur correction state at the telephoto end. Of the lateral aberration diagrams in the basic state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the lateral aberration at the image point of -70% of the maximum image height. Respectively. In each lateral aberration diagram in the image blur correction state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the image point at −70% of the maximum image height. Each corresponds to lateral aberration. In each lateral aberration diagram, the horizontal axis represents the distance from the principal ray on the pupil plane, the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line ( C-line) characteristics. In each lateral aberration diagram, the meridional plane is a plane including the optical axis of the first lens group G1 and the optical axis of the second lens group G2.

In the zoom lens system of each example, the moving amount (Y _T ) in the direction perpendicular to the optical axis of the second lens group G2 in the image blur correction state at the telephoto end is 0.080 mm. Corrects image blurring when the zoom lens system is tilted approximately 0.6 °.

  When the shooting distance is ∞ and the zoom lens system is tilted by about 0.6 ° at the telephoto end, the image decentering amount is when the entire second lens group G2 is translated by the above value in the direction perpendicular to the optical axis. Is equal to the amount of image eccentricity.

As can be seen from the respective lateral aberration diagrams, the symmetry of the lateral aberration at the axial image point is good. In addition, when the lateral aberration at the + 70% image point and the lateral aberration at the -70% image point are compared in the basic state, the curvature is small and the inclinations of the aberration curves are almost equal. It can be seen that the aberration is small. This means that sufficient imaging performance is obtained even in the image blur correction state. When the image blur correction angle of the zoom lens system is the same, the amount of parallel movement required for image blur correction decreases as the focal length of the entire zoom lens system decreases. Therefore, sufficient image blur correction can be performed for image blur correction angles up to about 0.6 ° at any zoom position.
(Numerical example 1)
The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. Table 1 shows surface data of the zoom lens system of Numerical Example 1, Table 2 shows aspheric data, Table 3 shows various data, Table 4 shows single lens data, Table 5 shows zoom lens group data, and Zoom Lens Group magnification is shown in Table 6.
Table 1 (surface data)
Surface number rd nd vd
Object ∞
1 * -1390.43200 0.30000 1.85400 40.4
2 * 5.24250 2.14710
3 10.45010 1.46010 2.00272 19.3
4 22.70850 Variable
5 * 6.44900 1.42800 1.85400 40.4
6 28.29370 0.15000
7 5.85410 1.68350 1.61800 63.4
8 14.51540 0.01000 1.56732 42.8
9 14.51540 0.30000 1.92286 20.9
10 3.97860 0.75680
11 24.67340 0.84720 1.83481 42.7
12 -24.67340 0.35800
13 (Aperture) ∞ Variable
14 * 42.39290 1.32510 1.52996 55.8
15 * -14.47050 variable
16 ∞ 0.78000 1.51680 64.2
17 ∞ BF
Image plane ∞
Table 2 (Aspheric data)
First side
K = 0.00000E + 00, A4 = -1.68007E-04, A6 = -8.77845E-06, A8 = 1.23266E-06
A10 = -5.20387E-08, A12 = 1.07019E-09, A14 = -1.05296E-11, A16 = 3.68983E-14
Second side
K = -5.32176E-01, A4 = -3.67160E-04, A6 = -1.79568E-05, A8 = 3.18558E-07
A10 = 1.40007E-07, A12 = -1.10285E-08, A14 = 3.22296E-10, A16 = -3.42850E-12
5th page
K = 1.11222E + 00, A4 = -7.88643E-04, A6 = -2.40130E-05, A8 = 2.37175E-07
A10 = -3.06417E-07, A12 = 2.75324E-08, A14 = -1.11864E-09, A16 = 0.00000E + 00
14th page
K = 0.00000E + 00, A4 = 2.33041E-03, A6 = -4.41401E-04, A8 = 3.60218E-05
A10 = -7.61600E-07, A12 = -7.35155E-08, A14 = 4.45249E-09, A16 = -6.68056E-11
15th page
K = 0.00000E + 00, A4 = 2.59658E-03, A6 = -3.01212E-04, A8 = 1.86266E-06
A10 = 2.74784E-06, A12 = -2.55886E-07, A14 = 9.07747E-09, A16 = -1.11168E-10
Table 3 (various data)
Zoom ratio 4.76425
Wide angle Medium telephoto Focal length 4.4000 9.5028 20.9629
F number 2.09665 3.67183 6.00036
Angle of view 43.3578 22.5565 10.3459
Image height 3.5000 3.9000 3.9000
Total lens length 34.0590 30.0725 38.9997
BF 0.52922 0.49873 0.46305
d4 14.8886 4.9187 0.3000
d13 3.9971 9.8281 23.3708
d15 3.0983 3.2812 3.3200
Entrance pupil position 6.8243 5.7280 4.8929
Exit pupil position -9.8438 -25.4307 136.8054
Front principal point position 9.3580 11.7481 29.0790
Rear principal point position 29.6590 20.5697 18.0367
Table 4 (Single lens data)
Lens Start surface Focal length
1 1 -6.1151
2 3 18.2195
3 5 9.4950
4 7 14.7781
5 9 -6.0213
6 11 14.8942
7 14 20.5220
Table 5 (zoom lens group data)
Group Start surface Focal length Lens construction length Front principal point position Rear principal point position
1 1 -10.56733 3.90720 -0.74429 -0.06518
2 5 9.73965 5.53350 -1.27159 0.83377
3 14 20.52204 1.32510 0.65095 1.10290
Table 6 (zoom lens group magnification)
Zoom lens group magnification Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 5 -0.52884 -1.15301 -2.54401
3 14 0.78735 0.77993 0.77977
(Numerical example 2)
The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. Surface data of the zoom lens system of Numerical Example 2 are shown in Table 7, aspherical data in Table 8, various data in Table 9, single lens data in Table 10, zoom lens group data in Table 11, and zoom lens. Group magnification is shown in Table 12.
Table 7 (surface data)
Surface number rd nd vd
Object ∞
1 * -33.10260 0.30000 1.85400 40.4
2 * 6.07210 2.05850
3 11.42170 1.47770 2.00272 19.3
4 32.30560 Variable
5 * 6.27570 1.24390 1.85400 40.4
6 38.16720 0.15000
7 5.66140 1.60260 1.61800 63.4
8 14.27780 0.01000 1.56732 42.8
9 14.27780 0.30000 1.92286 20.9
10 3.73470 0.78050
11 29.16480 0.76210 1.83481 42.7
12 -29.16480 0.37590
13 (Aperture) ∞ Variable
14 * 97.93100 1.49170 1.52996 55.8
15 * -10.34580 variable
16 ∞ 0.78000 1.51680 64.2
17 ∞ BF
Image plane ∞
Table 8 (Aspheric data)
First side
K = 0.00000E + 00, A4 = 4.13917E-04, A6 = -1.86745E-05, A8 = 1.22462E-06
A10 = -5.03789E-08, A12 = 1.08018E-09, A14 = -1.10957E-11, A16 = 4.05085E-14
Second side
K = -3.22898E-01, A4 = 7.95628E-05, A6 = -1.01897E-05, A8 = -3.52253E-07
A10 = 1.47626E-07, A12 = -1.10193E-08, A14 = 3.21327E-10, A16 = -3.40384E-12
5th page
K = 1.00094E + 00, A4 = -8.26041E-04, A6 = -1.97895E-05, A8 = -2.88908E-07
A10 = -2.64266E-07, A12 = 2.59771E-08, A14 = -1.11864E-09, A16 = 0.00000E + 00
14th page
K = 0.00000E + 00, A4 = 1.24727E-03, A6 = -3.44957E-04, A8 = 3.30748E-05
A10 = -8.05110E-07, A12 = -6.88306E-08, A14 = 4.51676E-09, A16 = -7.24210E-11
15th page
K = 0.00000E + 00, A4 = 1.53763E-03, A6 = -2.11662E-04, A8 = -2.83015E-07
A10 = 2.74982E-06, A12 = -2.54578E-07, A14 = 9.09640E-09, A16 = -1.13288E-10
Table 9 (various data)
Zoom ratio 4.76432
Wide angle Medium telephoto Focal length 4.4000 9.5666 20.9629
F number 2.24521 3.67130 6.00099
Angle of view 43.4163 22.4515 10.3472
Image height 3.5000 3.9000 3.9000
Total lens length 34.0225 29.9360 39.0583
BF 0.49285 0.47157 0.51838
d4 15.1655 4.9445 0.3000
d13 3.9530 9.9099 23.5870
d15 3.0782 3.2771 3.3200
Entrance pupil position 6.8149 5.6499 4.7778
Exit pupil position -10.3400 -31.4626 60.5688
Front principal point position 9.4278 12.3506 33.0586
Rear principal point position 29.6225 20.3693 18.0954
Table 10 (Single lens data)
Lens Start surface Focal length
1 1 -5.9870
2 3 17.0175
3 5 8.6395
4 7 14.1731
5 9 -5.5563
6 11 17.5724
7 14 17.7412
Table 11 (zoom lens group data)
Group Start surface Focal length Lens construction length Front principal point position Rear principal point position
1 1 -10.91208 3.83620 -0.94983 -0.35324
2 5 9.87229 5.22500 -1.67818 0.45103
3 14 17.74121 1.49170 0.88606 1.39809
Table 12 (zoom lens group magnification)
Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 5 -0.52746 -1.16205 -2.56353
3 14 0.76445 0.75444 0.74938
(Numerical Example 3)
The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. Surface data of the zoom lens system of Numerical Example 3 are shown in Table 13, aspherical data in Table 14, various data in Table 15, single lens data in Table 16, zoom lens group data in Table 17, and zoom lens. Group magnification is shown in Table 18.
Table 13 (surface data)
Object ∞
1 * -753.43420 0.30000 1.85400 40.4
2 * 5.59420 2.08400
3 10.02410 1.42950 2.00272 19.3
4 18.94560 Variable
5 * 5.73030 1.39380 1.85872 33.4
6 19.34380 0.15000
7 6.04300 1.33210 1.61752 63.5
8 16.71270 0.01000 1.56732 42.8
9 16.71270 0.30000 1.92524 20.3
10 3.93030 0.95620
11 16.79380 0.86910 1.83481 42.7
12 -35.20510 0.36590
13 (Aperture) ∞ Variable
14 * 615.70670 1.30010 1.52996 55.8
15 * -13.54000 variable
16 ∞ 0.78000 1.51680 64.2
17 ∞ BF
Image plane ∞
Table 14 (Aspheric data)
First side
K = 0.00000E + 00, A4 = 9.12955E-05, A6 = -1.63425E-05, A8 = 1.25386E-06
A10 = -4.99474E-08, A12 = 1.06982E-09, A14 = -1.15054E-11, A16 = 4.77355E-14
Second side
K = -4.00644E-01, A4 = -1.12412E-04, A6 = -1.78344E-05, A8 = -2.31254E-07
A10 = 1.54050E-07, A12 = -1.09996E-08, A14 = 3.14531E-10, A16 = -3.29481E-12
5th page
K = 8.42205E-01, A4 = -8.72182E-04, A6 = -2.52400E-05, A8 = -1.08306E-06
A10 = -2.56795E-07, A12 = 2.61649E-08, A14 = -1.31824E-09, A16 = 0.00000E + 00
14th page
K = 0.00000E + 00, A4 = 1.34885E-03, A6 = -3.18361E-04, A8 = 3.08821E-05
A10 = -9.38308E-07, A12 = -4.86636E-08, A14 = 3.77187E-09, A16 = -6.27040E-11
15th page
K = 0.00000E + 00, A4 = 1.40392E-03, A6 = -1.57204E-04, A8 = -5.92299E-06
A10 = 3.03973E-06, A12 = -2.70863E-07, A14 = 9.88991E-09, A16 = -1.27436E-10
Table 15 (various data)
Zoom ratio 5.66427
Wide angle Medium telephoto Focal length 4.4000 10.4157 24.9226
F number 2.09861 3.67090 6.00037
Angle of view 43.3853 20.6556 8.7308
Image height 3.5000 3.9000 3.9000
Total lens length 35.8386 31.3299 43.0068
BF 0.53294 0.50129 0.46912
d4 16.5392 4.9719 0.3000
d13 3.5155 10.3647 27.6470
d15 3.9803 4.2213 3.3200
Entrance pupil position 7.1986 5.8910 4.9772
Exit pupil position -9.7749 -25.0218 201.9542
Front principal point position 9.7204 12.0561 32.9826
Rear principal point position 31.4387 20.9142 18.0842
Table 16 (single lens data)
Lens Start surface Focal length
1 1 -6.5011
2 3 19.6526
3 5 9.0537
4 7 14.6310
5 9 -5.6174
6 11 13.7242
7 14 25.0172
Table 17 (Zoom lens group data)
Group Start surface Focal length Lens construction length Front principal point position Rear principal point position
1 1 -10.81945 3.81350 -0.57864 0.17562
2 5 10.12484 5.37710 -0.99637 0.76265
3 14 25.01724 1.30010 0.83207 1.28180
Table 18 (zoom lens group magnification)
Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 5 -0.50942 -1.21868 -2.78452
3 14 0.79831 0.78994 0.82725
(Numerical example 4)
The zoom lens system of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. The surface data of the zoom lens system of Numerical Example 4 is shown in Table 19, the aspheric data is shown in Table 20, the various data is shown in Table 21, the single lens data is shown in Table 22, the zoom lens group data is shown in Table 23, and the zoom lens. Group magnification is shown in Table 24.
Table 19 (surface data)
Surface number rd nd vd
Object ∞
1 * -753.43420 0.30000 1.85400 40.4
2 * 5.04020 2.35070
3 10.19810 1.43820 2.00272 19.3
4 21.00960 Variable
5 * 5.66400 1.49320 1.86305 32.1
6 18.64450 0.15000
7 6.17450 1.44280 1.59282 68.6
8 19.27300 0.01000 1.56732 42.8
9 19.27300 0.30000 1.93091 19.7
10 3.94630 0.73900
11 17.51640 0.93600 1.83481 42.7
12 -25.56070 0.35280
13 (Aperture) ∞ Variable
14 * 41.86370 1.40640 1.52996 55.8
15 * -13.59330 Variable
16 ∞ 0.78000 1.51680 64.2
17 ∞ BF
Image plane ∞
Table 20 (Aspheric data)
First side
K = 0.00000E + 00, A4 = 3.75594E-05, A6 = -1.47660E-05, A8 = 1.25737E-06
A10 = -5.04797E-08, A12 = 1.07000E-09, A14 = -1.14751E-11, A16 = 4.84034E-14
Second side
K = -5.85000E-01, A4 = -1.85138E-04, A6 = -1.68182E-05, A8 = -1.41910E-07
A10 = 1.55208E-07, A12 = -1.11459E-08, A14 = 3.17236E-10, A16 = -3.31645E-12
5th page
K = 8.05932E-01, A4 = -9.06568E-04, A6 = -2.41560E-05, A8 = -1.76632E-06
A10 = -1.63064E-07, A12 = 2.26930E-08, A14 = -1.42060E-09, A16 = 0.00000E + 00
14th page
K = 0.00000E + 00, A4 = 1.71563E-03, A6 = -3.28998E-04, A8 = 3.07558E-05
A10 = -9.58045E-07, A12 = -4.77775E-08, A14 = 3.70820E-09, A16 = -6.12079E-11
15th page
K = 0.00000E + 00, A4 = 1.82864E-03, A6 = -1.68338E-04, A8 = -6.37419E-06
A10 = 3.04170E-06, A12 = -2.71942E-07, A14 = 9.97560E-09, A16 = -1.29802E-10
Table 21 (various data)
Zoom ratio 5.01440
Wide angle Medium telephoto Focal length 4.0333 9.0151 20.2244
F number 2.57200 4.63417 6.01189
Angle of view 45.9103 23.6994 10.7159
Image height 3.5000 3.9000 3.9000
Total lens length 34.5093 31.1446 41.3798
BF 0.51452 0.48268 0.51000
d4 15.1985 5.1278 0.7089
d13 3.3743 10.0824 25.1418
d15 3.7229 3.7526 3.3200
Entrance pupil position 6.4868 5.4798 4.7510
Exit pupil position -9.6126 -28.5611 75.9675
Front principal point position 8.9138 11.6966 30.3960
Rear principal point position 30.4760 22.1295 21.1554
Table 22 (Single lens data)
Lens Start surface Focal length
1 1 -5.8616
2 3 18.5297
3 5 8.9495
4 7 14.7216
5 9 -5.3815
6 11 12.5747
7 14 19.5342
Table 23 (zoom lens group data)
Group Start surface Focal length Lens construction length Front principal point position Rear principal point position
1 1 -9.91777 4.08890 -0.75813 -0.12410
2 5 9.94751 5.42380 -1.15565 0.80363
3 14 19.53417 1.40640 0.70007 1.17908
Table 24 (zoom lens group magnification)
Group Start surface Wide angle Medium telephoto
1 1 0.00000 0.00000 0.00000
2 5 -0.54578 -1.21975 -2.66226
3 14 0.74511 0.74522 0.76597
Table 25 below shows corresponding values, ωW, and F-number for each condition in the zoom lens system of each numerical example.
Table 25 (corresponding values of conditions)

  The zoom lens system according to the present invention can be applied to digital input devices and camera systems such as digital cameras, mobile phone devices, PDAs (Personal Digital Assistance), surveillance cameras in surveillance systems, web cameras, in-vehicle cameras, etc. It is suitable for a photographing optical system that requires high image quality such as a camera.

G1 1st lens group G2 2nd lens group G3 3rd lens group L1 1st lens element L2 2nd lens element L3 3rd lens element L4 4th lens element L5 5th lens element L6 6th lens element L7 7th lens element L8 Parallel plate A Aperture stop S Image plane 1 Zoom lens system 2 Image sensor 3 Liquid crystal monitor 4 Case 5 Main barrel 6 Moving barrel 7 Cylindrical cam

Claims (10)

A zoom lens system having a plurality of lens groups each composed of at least one lens element, and having a negative power in order from the object side to the image side in sequence, a first lens group consisting of two lens elements And a second lens group having a positive power and a succeeding group having at least one refractive power, and the first lens group and the second lens during zooming from the wide-angle end to the telephoto end during imaging A zoom lens system that performs zooming by moving each lens group along the optical axis so that the distance from the group decreases.
The first lens group includes, in order from the object side, a biconcave lens element having a negative power and a meniscus lens element having a positive power and a convex surface facing the object side. A zoom lens system characterized in that an aperture stop that moves integrally with the second lens group on the optical axis is disposed on the image plane side of the second lens group, and satisfies the following condition (1): :
3.5 <fT / fW <10 (1)
here,
fW: focal length of the entire system at the wide-angle end fT: focal length of the entire system at the telephoto end,
It is. The zoom lens system according to claim 1, wherein the following condition (2) is satisfied:
0.3 <SF_L1 <1.0 (2)
(However, ωW> 35 °)
here,
SF_L1 = (R1 + R2) / (R1-R2)
R1: radius of curvature of the object side surface of the lens element having negative power arranged in the first lens group R2: radius of curvature of the image side surface of the lens element having negative power arranged in the first lens group ωW: Half value of maximum field angle at wide-angle end (°)
It is. 2. The zoom lens system according to claim 1, wherein the second lens group includes four lenses (where 1.6 <FNOW <2.8).
here,
FNOW: F number at the wide angle end.   2. The zoom lens system according to claim 1, wherein a lens surface closest to the image side of the second lens group has a convex shape toward the image surface side. The zoom lens system according to claim 1, satisfying the following condition (3):
0.00 <ts / fw <1.00 (3)
here,
ts: The distance between the lens surface closest to the image plane in the second lens group and the aperture stop.   The zoom lens system according to claim 1, wherein the first lens group includes at least one lens element having an aspherical surface.   The zoom lens system according to claim 1, wherein the biconcave lens element in the first lens group includes at least one aspheric surface.   The zoom lens system according to claim 1, wherein the second lens group is movable in a direction perpendicular to the optical axis.   An imaging apparatus comprising: the zoom lens system according to claim 1; and an output unit capable of outputting an optical image of an object as an electrical image signal. A camera system comprising: the zoom lens system according to claim 1; and an imaging device having an output unit capable of outputting an optical image of an object as an electrical image signal.

Images