JP2009169264A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure high performance and miniaturization after ensuring highly variable magnification. <P>SOLUTION: An aperture diaphragm is arranged adjacent to the object side of a third lens group, and the third lens group is composed of; a positive lens whose convex face is directed toward the object side; and a joined negative lens formed by joining a positive lens whose convex face is directed toward the object side, to a negative lens whose concave face is directed toward the image side. In this case, the following conditional equations (1) and (2) are satisfied: (1) 6<¾f3b¾/fw<10, and (2) 1.8<f1/(fw×ft)<SP>1/2</SP><2.2, wherein f3b represents the focal length of the joined negative lens which constitutes the third lens group, fw represents a focal length in a wide-angle end state, f1 represents the focal length of the first lens group, and ft represents a focal length in a telephoto end state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a zoom lens and an imaging apparatus. Specifically, the present invention relates to a technical field of a zoom lens and an imaging apparatus having a high zoom ratio of about 20 times.

  In an imaging device such as a lens-integrated still camera or a video camera without an interchangeable lens, the lens cannot be exchanged. Therefore, if the zoom ratio is low, it is difficult to deal with various shooting scenes. Therefore, in recent years, in an imaging apparatus that does not include an interchangeable lens, there is a high demand for zooming in on a zoom lens.

  Conventionally, zoom lenses that achieve such a high zoom ratio include those described in Patent Document 1 and Patent Document 2 below, for example.

  In the zoom lens described in Patent Document 1, the third lens group is composed of a biconvex positive lens and a meniscus negative lens with a concave surface facing the image side.

  In the zoom lens described in Patent Document 2, an aperture stop is disposed in the third lens group.

JP 2001-116997 A JP 2004-333769 A

  However, although the conventional zoom lens described above achieves high zooming, it is difficult to ensure high performance and miniaturization to improve image quality while ensuring high zooming. There is a problem to say.

  For example, in the zoom lens described in Patent Document 1, since the third lens group has a doublet configuration, it is difficult to correct on-axis aberrations and off-axis aberrations at the same time, and sufficient performance is improved. There is a problem that cannot be achieved.

  In the zoom lens described in Patent Document 2, the aperture stop is disposed in the third lens group, and the aperture stop exists at a position close to the image side. The off-axis light beam that passes through the two lens groups in sequence is separated from the optical axis, and there is a problem that it is difficult to reduce the diameter of the lens and to achieve sufficient size reduction.

  Accordingly, it is an object of the zoom lens and the imaging apparatus of the present invention to overcome the above-described problems and ensure high performance and miniaturization while ensuring high zooming.

In order to solve the above-described problem, the zoom lens has a first lens group having a positive refractive power and a second lens group having a negative refractive power arranged in order from the object side to the image side, and a positive refractive power. A third lens group and a fourth lens group having a positive refractive power, the first lens group and the third lens group being fixed in the optical axis direction, between the wide-angle end state and the telephoto end state The fourth lens group moves in the optical axis direction during zooming, and the fourth lens group compensates for variations in the image plane position due to the movement of the second lens group in the optical axis direction. Moved in the optical axis direction, an aperture stop is arranged adjacent to the object side of the third lens group, and the third lens group has a positive lens with a convex surface facing the object side and a convex surface facing the object side. The cemented negative lens, which consists of a positive lens and a negative lens with a concave surface facing the image side, is the object side. Are arranged in order toward the image side, in which so as to satisfy the following conditional expressions (1) and (2).
(1) 6 <| f3b | / fw <10
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state f1: focal length of the first lens group ft: focal length in the telephoto end state

  Therefore, the zoom lens can satisfactorily correct aberrations in the zoom region.

The zoom lens is preferably configured to satisfy the following conditional expression (3).
(3) 4 <f3 / fw
However,
f3: The focal length of the third lens group.

  By configuring so as to satisfy the conditional expression (3), it is possible to suppress a decrease in optical performance due to mutual decentering between the positive lens and the cemented negative lens constituting the third lens group.

The zoom lens is preferably configured to satisfy the following conditional expression (4).
(4) 4 <r3a / fw <5
However,
r3a: The radius of curvature of the object side lens surface of the positive lens disposed closest to the image side in the third lens group.

  By configuring so as to satisfy the conditional expression (4), the total length of the optical system is shortened without the convergence effect of the third lens group being weakened.

The zoom lens is preferably configured to satisfy the following conditional expression (5).
(5) 0.3 <| f2 | / (fw · ft) ^1/2 <0.39
However,
f2: The focal length of the second lens group.

  By configuring so as to satisfy the conditional expression (5), the amount of movement of the second lens unit is reduced while ensuring the necessary zoom ratio.

  In the zoom lens, the second lens group includes a meniscus first negative lens having a concave surface facing the image side, a second negative lens having a biconcave shape, a positive lens having a convex surface facing the object side, and a concave surface facing the image side. It is desirable that the third negative lens facing the lens is arranged in order from the object side to the image side.

  By adopting such a lens configuration for the second lens group, fluctuations in off-axis aberrations accompanying changes in the field angle and spherical aberrations accompanying changes in magnification are satisfactorily corrected.

  In the zoom lens, it is desirable that a positive lens and a third negative lens in the second lens group are cemented to form a cemented lens.

  By forming a cemented lens by the positive lens and the third negative lens of the second lens group, the occurrence of off-axis aberration is suppressed, and the fluctuation of off-axis aberration due to the change in the angle of view is corrected.

In order to solve the above-described problem, the imaging apparatus includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power, which are arranged in order from the object side to the image side. A third lens group and a fourth lens group having a positive refractive power, the first lens group and the third lens group being fixed in the optical axis direction, between the wide-angle end state and the telephoto end state The fourth lens group moves in the optical axis direction during zooming, and the fourth lens group compensates for variations in the image plane position due to the movement of the second lens group in the optical axis direction. Moved in the optical axis direction, an aperture stop is arranged adjacent to the object side of the third lens group, and the third lens group has a positive lens with a convex surface facing the object side and a convex surface facing the object side. A cemented negative lens composed of a positive lens and a negative lens with a concave surface facing the image side is imaged from the object side. To be arranged in order, in which so as to satisfy the following conditional expressions (1) and (2).
(1) 6 <| f3b | / fw <10
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state f1: focal length of the first lens group ft: focal length in the telephoto end state

  Therefore, in the imaging apparatus, it is possible to correct aberrations favorably in the zoom region of the zoom lens.

  In the zoom lens and the image pickup apparatus of the present invention, it is possible to ensure high performance and miniaturization while ensuring high zooming.

  The best mode for carrying out the zoom lens and the imaging apparatus of the present invention will be described below with reference to the drawings.

  The imaging apparatus of the present invention can be widely applied to various imaging apparatuses such as a still camera and a video camera, and various imaging apparatuses incorporated as a camera module in a personal computer, a PDA (Personal Digital Assistant), a mobile phone, and the like. In addition, the zoom lens of the present invention can be widely applied to various zoom lenses incorporated in these various imaging devices.

  First, the zoom lens of the present invention will be described.

  The zoom lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens disposed in order from the object side to the image side. A fourth lens group having a refractive power of 2nd lens, the first lens group and the third lens group being fixed in the optical axis direction, and the second lens during zooming between the wide-angle end state and the telephoto end state The fourth lens group moves in the optical axis direction so that the group moves in the optical axis direction and the fluctuation of the image plane position accompanying the movement of the second lens group in the optical axis direction. The third lens group is disposed adjacent to the object side of the lens group. The positive lens with the convex surface facing the object side is joined to the positive lens with the convex surface facing the object side and the negative lens with the concave surface facing the image side. The thus constructed cemented negative lens is arranged in order from the object side to the image side.

The zoom lens configured as described above satisfies the following conditional expressions (1) and (2).
(1) 6 <| f3b | / fw <10
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state f1: focal length of the first lens group ft: focal length in the telephoto end state

  In general, in a zoom lens, on the wide-angle end state, the axial light beam is incident on the third lens group in a state of being strongly diverged by the second lens group, so that axial aberration is likely to occur. Therefore, it is desirable to arrange the aperture stop near the center in the optical axis direction of the optical system.

  Therefore, in the zoom lens of the present invention, as described above, the aperture stop is disposed adjacent to the object side of the third lens group. By disposing the aperture stop adjacent to the object side of the third lens group, the third lens group is configured to mainly contribute to correction of axial aberration.

  In the zoom lens of the present invention, as described above, the second lens group disposed on the object side and the fourth lens group disposed on the image side are respectively moved in the optical axis direction with the aperture stop interposed therebetween. It is possible.

  By making the second lens group movable in the optical axis direction, the off-axis light beam passing through the second lens group passes away from the optical axis in the wide-angle end state, and changes from the wide-angle end state to the telephoto end state. Because the off-axis light beam approaches the optical axis, the off-axis aberration caused by the change in the position between the wide-angle end state and the telephoto end state of the lens due to the change in the height of the off-axis light beam passing through the second lens group. Can be corrected satisfactorily.

  By making the fourth lens group movable in the direction of the optical axis, the off-axis light beam passing through the fourth lens group is also separated from the optical axis when the position of the lens changes between the wide-angle end state and the telephoto end state. Therefore, it is possible to satisfactorily correct the fluctuation of off-axis aberration that occurs when the lens position changes.

  In the zoom lens of the present invention, since there is only one negative lens group (second lens group) between the first lens group and the fourth lens group, negative distortion occurring in the wide-angle end state is prevented. It is necessary to correct well, and the negative refracting power of the second lens group cannot be increased. However, in order to reduce the size by reducing the overall length of the optical system and the high zoom ratio, It is necessary to increase the negative refractive power.

  Therefore, in the zoom lens according to the present invention, as described above, the third lens group is constituted by the positive subgroup arranged on the object side and the negative subgroup arranged on the image side, so that An element having a negative refractive power is disposed on the image side. Therefore, the negative refractive power in the optical system can be increased, and both high zooming and miniaturization can be achieved.

  In the zoom lens of the present invention, as described above, the third lens group is composed of a positive lens group including a positive lens and a negative lens group including a positive lens and a negative lens. In this way, when the positive subgroup and the negative subgroup are configured as one lens group, the refractive power of the positive subgroup and the negative subgroup increases as the principal point distance between the positive subgroup and the negative subgroup decreases. Even a slight decentration that sometimes occurs may cause a significant decrease in optical performance, making it impossible to ensure stable optical performance.

  Therefore, in the zoom lens according to the present invention, as described above, the positive partial group of the third lens group is configured by a positive lens having a convex surface directed toward the object side, and the negative partial group of the third lens group is disposed on the object side. It is constituted by a cemented negative lens in which a positive lens having a convex surface and a negative lens having a concave surface facing the image side are cemented. By providing the cemented negative lens having such a configuration in the third lens group, the principal point position of the negative subgroup is moved to the image side, so that the principal point interval between the positive subgroup and the negative subgroup is widened, Stable optical performance can be ensured during manufacturing. Moreover, the thickness of the third lens group can be reduced by configuring the negative portion group as a cemented lens.

  Next, each conditional expression described above will be described.

As described above, the zoom lens according to the present invention is configured to satisfy the following conditional expression (1).
(1) 6 <| f3b | / fw <10
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state.

  Conditional expression (1) defines the focal length of the cemented negative lens disposed in the third lens group.

  When the value of | f3b | / fw exceeds the upper limit value of conditional expression (1), the refractive power of the negative subgroup becomes too small, so that the negative distortion occurring in the wide-angle end state is sufficiently corrected. Cannot be obtained, and good imaging performance cannot be obtained. Although it is possible to correct negative distortion by weakening the refractive power of the second lens group, if the refractive power of the second lens group is weakened, the total length of the optical system becomes longer and the first lens group This is not preferable because it increases the size.

  When the value of | f3b | / fw falls below the lower limit value of the conditional expression (1), the refractive power of the negative subgroup becomes too large, so that the positive lens and the cemented negative lens constituting the third lens group The optical performance is remarkably deteriorated due to the mutual eccentricity, and it becomes difficult to ensure stable optical performance at the time of manufacture.

  Therefore, in the zoom lens according to the present invention, by satisfying the conditional expression (1), it is possible to sufficiently correct the negative distortion occurring in the wide-angle end state to obtain a good imaging performance and to obtain a positive image. Stable optical performance can be ensured at the time of manufacture by suppressing a decrease in optical performance due to mutual eccentricity between the lens and the cemented negative lens.

As described above, the zoom lens according to the present invention is configured to satisfy the following conditional expression (2).
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f1: focal length of the first lens group ft: focal length in the telephoto end state.

  Conditional expression (2) defines the focal length of the first lens group.

  Since the first lens group is disposed away from the image plane position, the lens diameter tends to increase. In order to reduce the lens diameter of the first lens group, it is effective to weaken the refractive power of the first lens group. However, if the refractive power of the first lens group is weakened, the total length of the optical system tends to be long. Conversely, to shorten the overall length of the optical system, it is effective to increase the refractive power of the first lens group, but the lens diameter of the first lens group becomes large. Accordingly, in order to reduce the lens diameter of the first lens group and shorten the overall length of the optical system, it is necessary to appropriately set the refractive power of the first lens group.

When the value of f1 / (fw · ft) ^1/2 exceeds the upper limit value of the conditional expression (2), the total length of the optical system becomes long, and the zoom lens cannot be reduced in size.

Conversely, if the value of f1 / (fw · ft) ^1/2 falls below the lower limit value of conditional expression (2), the negative spherical aberration generated in the first lens group in the telephoto end state is sufficiently corrected. This makes it impossible to secure stable optical performance in the telephoto end state.

  Therefore, in the zoom lens of the present invention, by satisfying conditional expression (2), the zoom lens can be miniaturized by shortening the total length of the optical system, and stable optical performance in the telephoto end state can be achieved. Can be secured.

  In the zoom lens according to the present invention, by configuring as described above, it is possible to ensure high performance and miniaturization while ensuring high zooming.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (3) is satisfied.
(3) 4 <f3 / fw
However,
f3: The focal length of the third lens group.

  Conditional expression (3) defines the focal length of the third lens group.

  When the value of f3 / fw falls below the lower limit value of conditional expression (3), the optical performance is remarkably deteriorated due to mutual decentering between the positive lens and the cemented negative lens constituting the third lens group. Sometimes it becomes difficult to ensure stable optical performance.

  Therefore, in the zoom lens according to the embodiment of the present invention, by satisfying the conditional expression (3), the optical performance is deteriorated due to the mutual eccentricity of the positive lens and the cemented negative lens constituting the third lens group. Stable optical performance can be ensured at the time of manufacture.

In the zoom lens according to an embodiment of the present invention, in order to further reduce the size, conditional expression (3) is set to less than 5 and the following conditional expression (3) ′ is satisfied. It is desirable to configure as follows.
(3) '4 <f3 / fw <5
However,
f3: The focal length of the third lens group.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (4) is satisfied.
(4) 4 <r3a / fw <5
However,
r3a: The radius of curvature of the object side lens surface of the positive lens disposed closest to the image side in the third lens group.

  Conditional expression (4) is an expression for defining the radius of curvature of the lens surface closest to the object side in the third lens group, and is an expression for achieving a balance between high performance and miniaturization.

  When the value of r3a / fw exceeds the upper limit value of conditional expression (4), the principal point position of the positive lens moves to the image side, so that the convergence action is weakened and the entire length of the optical system is lengthened.

  Conversely, when the value of r3a / fw falls below the lower limit value of conditional expression (4), the negative spherical aberration occurring in the positive lens (positive subgroup) cannot be corrected sufficiently, and In order to compensate for this, the positive spherical aberration generated in the cemented negative lens also increases, so that the optical performance is remarkably deteriorated even by a slight decentration occurring during manufacturing.

  Therefore, in the zoom lens according to the embodiment of the present invention, by satisfying the conditional expression (4), the total length of the optical system is shortened without the convergence effect being weakened, and the slight eccentricity generated during the manufacturing process. It is possible to prevent the optical performance from being degraded.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (5) is satisfied.
(5) 0.3 <| f2 | / (fw · ft) ^1/2 <0.39
However,
f2: The focal length of the second lens group.

  Conditional expression (5) defines the focal length of the second lens group.

When | f2 | / (fw · ft) ^1/2 exceeds the upper limit value of the conditional expression (5), the negative refractive power of the second lens group becomes too small, and a predetermined zoom ratio is obtained. Therefore, the amount of movement of the second lens group necessary for this increases, and the overall length of the optical system increases.

On the contrary, when | f2 | / (fw · ft) ^1/2 falls below the lower limit value of the conditional expression (5), the negative refractive power of the second lens group becomes too large. Off-axis light beam passing through the second lens group approaches the optical axis when changing from the wide-angle end state to the telephoto end state, and passes through the second lens group regardless of the lens position state from the wide-angle end state to the telephoto end state. The change in the height of the light beam becomes small, and the fluctuation of the off-axis aberration that occurs when the lens position changes can not be sufficiently corrected, making it difficult to achieve higher performance.

  Therefore, in the zoom lens according to the embodiment of the present invention, by satisfying the conditional expression (5), the amount of movement of the second lens unit necessary for obtaining a predetermined zoom ratio can be reduced and optical The total length of the system can be shortened, and the off-axis aberration caused by the change in the position between the wide-angle end state and the telephoto end state of the lens due to the change in the height of the off-axis light beam passing through the second lens group. The fluctuation can be corrected satisfactorily.

  In the zoom lens according to the embodiment of the present invention, the second lens group includes a meniscus negative lens having a concave surface facing the image side, a negative lens having a biconcave shape, and a positive lens having a convex surface facing the object side. It is desirable that the negative lens with the concave surface facing the image side is arranged in order from the object side to the image side.

  The second lens group is a lens group responsible for a zooming action, and it is necessary to properly correct the fluctuation of off-axis aberrations accompanying a change in the angle of view and to correct the fluctuation of spherical aberrations accompanying a change in magnification.

  Therefore, by configuring the second lens group as described above, the aberration correction function of each lens constituting the second lens group is clarified, and the variation in spherical aberration can be corrected well.

  Specifically, a negative meniscus lens having a concave surface facing the image side is disposed on the most object side of the second lens group, thereby suppressing off-axis aberrations and off-axis aberrations accompanying changes in the field angle. This corrects for fluctuations. Further, on the image side of the negative lens arranged closest to the object side, a negative lens, a positive lens, and a negative lens are arranged in order so that the negative lens is arranged at a symmetrical position with the positive lens interposed therebetween. Because of the triplet configuration, it is possible to satisfactorily correct the variation in spherical aberration accompanying the change in magnification.

  In the zoom lens according to the embodiment of the present invention, in order to improve performance by suppressing the decentration between the lenses due to manufacturing errors, the zoom lens is closest to the positive lens constituting the second lens group. It is desirable to form a cemented lens by cementing the negative lens to be disposed.

  In the zoom lens according to the embodiment of the present invention, the fifth lens group is disposed on the image side of the fourth lens group, and the fifth lens group is disposed on the negative lens and the image side thereof with an air space therebetween. It is possible to adopt a configuration having at least one positive lens.

  The fifth lens group has an effect of adjusting the exit pupil position and an effect of correcting negative distortion that is likely to occur in the wide-angle end state.

  When recording an object image using an imaging element in an imaging device, it is necessary to appropriately set the exit pupil position. Depending on the exit pupil position, the position of the aperture stop or the lens group arranged on the image side of the aperture stop There may be restrictions on the refractive power arrangement.

  Therefore, in the zoom lens according to the embodiment of the present invention, as described above, the fifth lens group is configured by the negative lens and the positive lens disposed on the image side thereof, whereby the exit pupil position is defined as an image. It is possible to set the position far from the surface to make the chief ray almost parallel to the optical axis, reducing the restrictions on the position of the aperture stop and the refractive power arrangement of the lens group arranged on the image side of the aperture stop. In addition, the exit pupil position can be set appropriately. In addition, since the fifth lens group is composed of a negative lens and a positive lens disposed on the image side, the on-axis light beam and the off-axis light beam are separated from each other, so that the negative distortion is favorably corrected. It becomes possible.

  In the zoom lens according to the embodiment of the present invention, the fourth lens group includes a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side arranged in order from the object side to the image side. It is desirable to have a configuration.

  By adopting such a doublet configuration for the fourth lens group, it is possible to correct off-axis aberrations and on-axis aberrations at the same time, and to satisfactorily correct variations in various aberrations that occur when the subject position changes. be able to.

  In the zoom lens according to the embodiment of the present invention, it is desirable to use a glass material having high anomalous dispersion for the first lens group in order to suppress the occurrence of chromatic aberration.

  In particular, when a cemented lens having a positive lens is provided in the first lens group, by using a glass material having a high anomalous dispersion for the positive lens of the cemented lens, secondary dispersion generated at the center of the screen in the telephoto end state. Can be corrected satisfactorily.

  In the zoom lens according to an embodiment of the present invention, higher optical performance can be realized by using an aspheric lens. In particular, by using a lens having an aspheric surface in the third lens group, it is possible to improve the central performance. Further, by using a lens having an aspheric surface in the second lens group, it is possible to satisfactorily correct coma variation due to the angle of view that occurs in the wide-angle end state.

  Furthermore, higher optical performance can be ensured by using a plurality of aspheric surfaces in one optical system.

  In the zoom lens according to the embodiment of the present invention, by making one lens group of each lens group or one partial group of one lens group movable in a direction substantially perpendicular to the optical axis, It is possible to perform image blur correction.

  In particular, since the third lens group has a small lens diameter and is fixed in the optical axis direction, it is easy to dispose a drive mechanism that moves in the direction substantially perpendicular to the optical axis in the vicinity of the third lens group. Further, in the third lens group, as described above, since spherical aberration that occurs independently in the third lens group is also corrected well, when the third lens group is moved in a direction substantially orthogonal to the optical axis, The aberration fluctuations that occur in the lens can be reduced.

  Therefore, a driving system for moving the third lens group in a direction substantially orthogonal to the optical axis, a detection system for detecting image blur, and an amount of movement in a direction substantially orthogonal to the optical axis based on the output from the detection system The third lens group can function as an anti-vibration optical system by incorporating an arithmetic system for calculating the value into the imaging apparatus.

  As described above, when the fifth lens group is arranged in addition to the first to fourth lens groups, the direction in which the negative lens or the positive lens constituting the fifth lens group is substantially orthogonal to the optical axis. It becomes possible to move to. When the fifth lens group is moved in a direction substantially orthogonal to the optical axis, the amount of aberration fluctuation that occurs is small.

  Therefore, a driving system for moving the fifth lens group in a direction substantially orthogonal to the optical axis, a detection system for detecting image blur, and an amount of movement in a direction substantially orthogonal to the optical axis based on the output from the detection system It is also possible to make the fifth lens group function as an anti-vibration optical system by incorporating an arithmetic system for calculating the value into the imaging apparatus.

  In the zoom lens according to the embodiment of the present invention, a low-pass filter for preventing the occurrence of moire fringes is arranged on the image side of the lens system, or an infrared cut filter is arranged according to the spectral sensitivity characteristic of the light receiving element. Is possible.

  Next, specific embodiments of the zoom lens according to the present invention and numerical examples obtained by applying specific numerical values to the embodiments will be described with reference to the drawings and tables.

  In each embodiment, an aspherical surface is introduced, and the aspherical shape is defined by the following equation (1).

  In Equation 1, x is the sag amount, c is the curvature, y is the height from the optical axis, κ is the conic constant, A, B,... Are aspherical coefficients.

  FIG. 1 shows the refractive power distribution of the zoom lens 1 according to the first embodiment of the present invention. In the figure, W represents the wide-angle end state, and T represents the telephoto end state.

  The zoom lens 1 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens having a positive refractive power. A group G4 and a fifth lens group G5 having a positive refractive power are arranged in order from the object side to the image side. In the zoom lens 1, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed in the optical axis direction during zooming between the wide-angle end state and the telephoto end state. The second lens group G2 moves in the optical axis direction, and the fourth lens group G4 moves in the optical axis direction so as to correct the variation of the image plane position accompanying the movement of the second lens group G2 in the optical axis direction. To do. The fourth lens group G4 moves toward the object side when focusing on a short distance and moves toward the image side when focusing on a long distance.

  FIG. 2 is a diagram showing a lens configuration of the zoom lens 1 according to the first embodiment of the present invention.

  The first lens group G1 includes a cemented lens in which a meniscus negative lens L11 having a convex surface directed toward the object side and a positive lens L12 having a convex surface directed toward the object side are cemented, and a positive lens L13 having a convex surface directed toward the object side. A positive lens L14 having a convex surface facing the object side is arranged in order from the object side to the image side.

  The second lens group G2 includes a meniscus negative lens L21 having a concave surface facing the image side, a biconcave negative lens L22, a positive lens L23 having a convex surface facing the object side, and a negative lens L24 having a concave surface facing the image side. Are joined in order from the object side to the image side.

  The third lens group G3 includes a negative biconvex lens L31, a negative meniscus lens L32 having a convex surface facing the object side, and a negative meniscus lens L33 having a concave surface facing the image side. The lenses are arranged in order from the object side to the image side. The positive lens L31 constitutes a positive lens group, and the positive lens L32 and the negative lens L33 constitute a negative lens group.

  The fourth lens group G4 includes a cemented lens formed by cementing a biconvex positive lens L41 and a meniscus negative lens L42 having a concave surface directed toward the object side.

  The fifth lens group G5 includes a biconcave negative lens L51 and a biconvex positive lens L52 arranged in order from the object side to the image side.

  An aperture stop S is disposed adjacent to the object side of the third lens group G3, and the aperture stop S is fixed.

  A filter FL is disposed between the fifth lens group G5 and the image plane IP.

  Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the zoom lens 1 according to the first embodiment.

  In Table 1 and each table showing lens data described later, f represents a focal length, FNO represents an F number, and 2ω represents an angle of view. “Surface number” indicates the i-th surface (i is a natural number) counted from the object side, “curvature radius” indicates the curvature radius of the i-th surface counted from the object side, and “surface spacing” Indicates the axial upper surface distance between the i-th surface and the (i + 1) -th surface counted from the object side, and “refractive index” is the d-line (λ = 587.6 nm) of the glass material having the i-th surface on the object side. The “Abbe number” indicates the Abbe number with respect to the d-line of the glass material having the i-th surface on the object side. “0.0000” for the radius of curvature indicates that the surface is a flat surface, “(Di)” indicates that the surface interval is a variable interval, and “(Bf)” indicates the back surface distance. Indicates focus.

  In the zoom lens 1, the object side surface (16th surface) of the positive lens L31 in the third lens group G3 and the object side surface (21st surface) of the positive lens L41 in the fourth lens group G4 are formed as aspherical surfaces. ing. Therefore, Table 2 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D together with the conic constant κ in Numerical Example 1.

In Table 2 and each table showing an aspherical coefficient, which will be described later, “E-i” represents an exponential expression with 10 as a base, that is, “10 ⁻ⁱ ”, for example, “0.12345E-05”. "Represents" 0.12345 × 10 ^-5 ".

  In the zoom lens 1, during zooming between the wide-angle end state and the telephoto end state, the surface distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, and the third lens group G3. The surface distance D14 between the third lens group G3 and the fourth lens group G4, and the surface distance D23 between the fourth lens group G4 and the fifth lens group G5. Therefore, each value in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 7.510), and the telephoto end state (f = 18.781) of the distance between the surfaces in Numerical Example 1 is back-focused. It is shown in Table 3 together with Bf.

  Table 4 shows corresponding values of the conditional expressions (1) to (5) of the numerical value example 1.

  3 to 5 are graphs showing various aberrations in the infinite focus state in Numerical Example 1, FIG. 3 is a wide-angle end state (f = 1.000), and FIG. 4 is an intermediate focal length state (f = 7.510), FIG. 5 shows various aberration diagrams in the telephoto end state (f = 18.781).

  In each aberration diagram of FIGS. 3 to 5, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the lateral aberration diagram, “y” indicates the image height, and “A” indicates the angle of view.

  From the aberration diagrams of FIGS. 3 to 5, it is clear that Numerical Example 1 has excellent imaging performance with various aberrations corrected satisfactorily.

  FIG. 6 is a diagram showing a lens configuration of the zoom lens 2 according to the second embodiment of the present invention.

  As with the zoom lens 1, the zoom lens 2 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a positive lens. The fourth lens group G4 having refractive power and the fifth lens group G5 having positive refractive power are arranged in order from the object side to the image side. In the zoom lens 2, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed in the optical axis direction during zooming between the wide-angle end state and the telephoto end state. The second lens group G2 moves in the optical axis direction, and the fourth lens group G4 moves in the optical axis direction so as to correct the variation of the image plane position accompanying the movement of the second lens group G2 in the optical axis direction. To do. The fourth lens group G4 moves toward the object side when focusing on a short distance and moves toward the image side when focusing on a long distance.

  The first lens group G1 includes a cemented lens in which a meniscus negative lens L11 having a convex surface directed toward the object side and a positive lens L12 having a convex surface directed toward the object side are cemented, and a positive lens L13 having a convex surface directed toward the object side. A positive lens L14 having a convex surface facing the object side is arranged in order from the object side to the image side.

  The second lens group G2 includes a meniscus negative lens L21 having a concave surface facing the image side, a biconcave negative lens L22, a positive lens L23 having a convex surface facing the object side, and a negative lens L24 having a concave surface facing the image side. Are joined in order from the object side to the image side.

  The third lens group G3 includes a negative biconvex lens L31, a negative meniscus lens L32 having a convex surface facing the object side, and a negative meniscus lens L33 having a concave surface facing the image side. The lenses are arranged in order from the object side to the image side. The positive lens L31 constitutes a positive lens group, and the positive lens L32 and the negative lens L33 constitute a negative lens group.

  The fourth lens group G4 includes a cemented lens formed by cementing a biconvex positive lens L41 and a meniscus negative lens L42 having a concave surface directed toward the object side.

  The fifth lens group G5 includes a biconcave negative lens L51 and a biconvex positive lens L52 arranged in order from the object side to the image side.

  An aperture stop S is disposed adjacent to the object side of the third lens group G3, and the aperture stop S is fixed.

  A filter FL is disposed between the fifth lens group G5 and the image plane IP.

  Table 5 shows lens data of Numerical Example 2 in which specific numerical values are applied to the zoom lens 2 according to the second embodiment.

  In the zoom lens 2, the object side surface (16th surface) of the positive lens L31 in the third lens group G3 and the object side surface (21st surface) of the positive lens L41 in the fourth lens group G4 are formed as aspherical surfaces. ing. Therefore, Table 6 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients A, B, C, and D in Numerical Example 2 together with the conic constant κ.

  In the zoom lens 2, upon zooming between the wide-angle end state and the telephoto end state, the surface distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, and the third lens group G3. The surface distance D14 between the third lens group G3 and the fourth lens group G4, and the surface distance D23 between the fourth lens group G4 and the fifth lens group G5. Therefore, each value in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 7.262), and the telephoto end state (f = 18.780) of the distance between the surfaces in Numerical Example 2 is back-focused. It shows in Table 7 with Bf.

  Table 8 shows corresponding values of the conditional expressions (1) to (5) in the numerical value example 2.

  7 to 9 are graphs showing various aberrations in the infinite focus state in Numerical Example 2, FIG. 7 is a wide-angle end state (f = 1.000), and FIG. 8 is an intermediate focal length state (f = 7.262), FIG. 9 shows various aberration diagrams in the telephoto end state (f = 18.780).

  In each aberration diagram of FIGS. 7 to 9, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the lateral aberration diagram, “y” indicates the image height, and “A” indicates the angle of view.

  From the aberration diagrams of FIGS. 7 to 9, it is clear that Numerical Example 2 has excellent image forming performance with various aberrations corrected well.

  FIG. 10 shows the refractive power distribution of the zoom lens 3 according to the third embodiment of the present invention. In the figure, W represents the wide-angle end state, and T represents the telephoto end state.

  The zoom lens 3 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens having a positive refractive power. The group G4 is arranged in order from the object side to the image side. In the zoom lens 3, the first lens group G1 and the third lens group G3 are fixed in the optical axis direction during zooming between the wide-angle end state and the telephoto end state, and the second lens group G2 moves in the optical axis direction, and the fourth lens group G4 moves in the optical axis direction so as to correct the variation in the image plane position accompanying the movement of the second lens group G2 in the optical axis direction. The fourth lens group G4 moves toward the object side when focusing on a short distance and moves toward the image side when focusing on a long distance.

  FIG. 11 is a diagram showing a lens configuration of the zoom lens 3 according to the third embodiment of the present invention.

  The first lens group G1 includes a cemented lens in which a meniscus negative lens L11 having a convex surface directed toward the object side and a positive lens L12 having a convex surface directed toward the object side are cemented, and a positive lens L13 having a convex surface directed toward the object side. A positive lens L14 having a convex surface facing the object side is arranged in order from the object side to the image side.

  The second lens group G2 includes a meniscus negative lens L21 having a concave surface facing the image side, a biconcave negative lens L22, a positive lens L23 having a convex surface facing the object side, and a negative lens L24 having a concave surface facing the image side. Are joined in order from the object side to the image side.

  The third lens group G3 includes a negative biconvex lens L31, a negative meniscus lens L32 having a convex surface facing the object side, and a negative meniscus lens L33 having a concave surface facing the image side. The lenses are arranged in order from the object side to the image side. The positive lens L31 constitutes a positive lens group, and the positive lens L32 and the negative lens L33 constitute a negative lens group.

  The fourth lens group G4 includes a cemented lens formed by cementing a biconvex positive lens L41 and a meniscus negative lens L42 having a concave surface directed toward the object side.

  An aperture stop S is disposed adjacent to the object side of the third lens group G3, and the aperture stop S is fixed.

  A filter FL is disposed between the fourth lens group G4 and the image plane IP.

  Table 9 shows lens data of a numerical example 3 in which specific numerical values are applied to the zoom lens 3 according to the third embodiment.

  In the zoom lens 3, the object side surface (16th surface) of the positive lens L31 in the third lens group G3 and the object side surface (21st surface) of the positive lens L41 in the fourth lens group G4 are formed as aspherical surfaces. ing. Therefore, Table 10 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients A, B, C, and D together with the conic constant κ in Numerical Example 3.

  In the zoom lens 3, during zooming between the wide-angle end state and the telephoto end state, the surface distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, and the third lens group G3. The surface distance D14 between the third lens group G3 and the fourth lens group G4, and the surface distance D23 between the fourth lens group G4 and the filter FL. Therefore, each value in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 6.537), and the telephoto end state (f = 18.765) of the distance between the surfaces in Numerical Example 3 is back-focused. It shows in Table 11 with Bf.

  Table 12 shows corresponding values of the conditional expressions (1) to (5) in the numerical value example 3.

  12 to 14 are graphs showing various aberrations in the infinite focus state in Numerical Example 3, FIG. 12 is a wide-angle end state (f = 1.000), and FIG. 13 is an intermediate focal length state (f = 6.537), FIG. 14 shows various aberration diagrams in the telephoto end state (f = 18.765).

  In each aberration diagram of FIGS. 12 to 14, a solid line in the astigmatism diagram indicates a sagittal image plane, and a broken line indicates a meridional image plane. In the lateral aberration diagram, “y” indicates the image height, and “A” indicates the angle of view.

  From the respective aberration diagrams of FIGS. 12 to 14, it is apparent that Numerical Example 3 has excellent imaging performance with various aberrations corrected satisfactorily.

  Next, the imaging apparatus of the present invention will be described.

  The imaging apparatus of the present invention includes a zoom lens and an imaging element that converts an optical image formed by the zoom lens into an electrical signal. The imaging apparatus includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, in which the zoom lens is disposed in order from the object side to the image side. And a fourth lens group having a positive refractive power, the first lens group and the third lens group are fixed in the optical axis direction, and the first lens group and the fourth lens group are zoomed between the wide-angle end state and the telephoto end state. The second lens group is moved in the optical axis direction, and the fourth lens group is moved in the optical axis direction so as to compensate for the fluctuation of the image plane position accompanying the movement of the second lens group in the optical axis direction. The third lens group is disposed adjacent to the object side of the three lens groups. The third lens group includes a positive lens having a convex surface facing the object side, a positive lens having a convex surface facing the object side, and a negative lens having a concave surface facing the image side. And a cemented negative lens formed by cementing are arranged in order from the object side to the image side.

The zoom lens in the imaging apparatus configured as described above satisfies the following conditional expressions (1) and (2).
(1) 6 <| f3b | / fw <10
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state f1: focal length of the first lens group ft: focal length in the telephoto end state

  In general, in a zoom lens in an imaging apparatus, on the wide-angle end state, an axial light beam is incident on the third lens group in a state of being strongly diverged by the second lens group, and thus axial aberration is likely to occur. Therefore, it is desirable to arrange the aperture stop near the center in the optical axis direction of the optical system.

  Therefore, in the imaging apparatus of the present invention, as described above, the aperture stop is arranged adjacent to the object side of the third lens group. By disposing the aperture stop adjacent to the object side of the third lens group, the third lens group is configured to mainly contribute to correction of axial aberration.

  In the imaging apparatus of the present invention, as described above, the second lens group disposed on the object side and the fourth lens group disposed on the image side are moved in the optical axis direction with the aperture stop interposed therebetween. It is possible.

  By making the second lens group movable in the optical axis direction, the off-axis light beam passing through the second lens group passes away from the optical axis in the wide-angle end state, and changes from the wide-angle end state to the telephoto end state. Because the off-axis light beam approaches the optical axis, the off-axis aberration caused by the change in the position between the wide-angle end state and the telephoto end state of the lens due to the change in the height of the off-axis light beam passing through the second lens group. Can be corrected satisfactorily.

  By making the fourth lens group movable in the direction of the optical axis, the off-axis light beam passing through the fourth lens group is also separated from the optical axis when the position of the lens changes between the wide-angle end state and the telephoto end state. Therefore, it is possible to satisfactorily correct the fluctuation of off-axis aberration that occurs when the lens position changes.

  In the imaging apparatus according to the present invention, since there is only one negative lens group (second lens group) between the first lens group and the fourth lens group, negative distortion occurring in the wide-angle end state is prevented. It is necessary to correct well, and the negative refracting power of the second lens group cannot be increased. However, in order to reduce the size by reducing the overall length of the optical system with a high zoom ratio, negative refraction is required. It is necessary to strengthen the power.

  Therefore, in the imaging apparatus according to the present invention, as described above, the third lens group is constituted by the positive subgroup arranged on the object side and the negative subgroup arranged on the image side, thereby reducing the aperture stop. An element having a negative refractive power is disposed on the image side. Therefore, the negative refractive power in the optical system can be increased, and both high zooming and miniaturization can be achieved.

  In the imaging apparatus of the present invention, as described above, the third lens group is constituted by the positive lens group including the positive lens and the negative lens group including the positive lens and the negative lens. In this way, when the positive subgroup and the negative subgroup are configured as one lens group, the refractive power of the positive subgroup and the negative subgroup increases as the principal point distance between the positive subgroup and the negative subgroup decreases. Even a slight decentration that sometimes occurs may cause a significant decrease in optical performance, making it impossible to ensure stable optical performance.

  Therefore, in the imaging apparatus of the present invention, as described above, the positive subgroup of the third lens group is configured by a positive lens having a convex surface facing the object side, and the negative subgroup of the third lens group is set on the object side. It is constituted by a cemented negative lens in which a positive lens having a convex surface and a negative lens having a concave surface facing the image side are cemented. By providing the cemented negative lens having such a configuration in the third lens group, the principal point position of the negative subgroup is moved to the image side, so that the principal point interval between the positive subgroup and the negative subgroup is widened, Stable optical performance can be ensured during manufacturing. Moreover, the thickness of the third lens group can be reduced by configuring the negative portion group as a cemented lens.

  In addition, the image pickup apparatus of the present invention can satisfy the conditional expression (1) to sufficiently correct the negative distortion occurring in the wide-angle end state to obtain a good imaging performance and to join the positive lens. It is possible to secure a stable optical performance at the time of manufacture by suppressing a decrease in optical performance due to mutual decentration with the negative lens.

  Furthermore, the image pickup apparatus of the present invention can satisfy the conditional expression (2), thereby reducing the size of the zoom lens by shortening the total length of the optical system and ensuring stable optical performance in the telephoto end state. Can do.

  In the imaging apparatus of the present invention, by configuring as described above, it is possible to ensure high performance and miniaturization while ensuring high zooming.

  FIG. 15 shows a block diagram of an embodiment of the imaging apparatus of the present invention.

  The imaging device 10 is, for example, a digital still camera. The imaging unit 10 optically acquires a subject image, and converts the subject image acquired by the lens unit 20 into an electrical image signal as an optical image. And a camera body 30 having a function of performing various processes on the electrical image signal and controlling the lens unit 20.

  The lens unit 20 includes a zoom lens 21 composed of optical elements such as a lens and a filter, a zoom drive unit 22 that moves the movable lens group during zooming, a focus drive unit 23 that moves the movable lens group during focusing, and a shift during camera shake correction. A shift lens driving unit 24 that shifts the lens group in a direction having a component perpendicular to the optical axis and an iris driving unit 25 that controls the size of the aperture system of the aperture stop are provided.

  As the zoom lens 21, any one of the zoom lenses 1 to 3 described above, or the zoom lens of the present invention such as Numerical Example 1 to Numerical Example 3 can be applied.

  The camera body 30 includes an image sensor 31 that converts an optical image captured through the zoom lens 21 into an electrical image signal.

  For example, a charge coupled device (CCD), a complementary metal-oxide semiconductor (CMOS), or the like can be applied as the imaging element 31. The electrical image signal output from the image pickup device 31 is subjected to various processes by the image processing circuit 32, and then data compressed by a predetermined method and temporarily stored in the image memory 33 as image data.

  A camera control CPU (Central Processing Unit) 34 has a function of controlling the entire camera body 30 and the lens unit 20, reads image data temporarily stored in the image memory 33, and displays a liquid crystal display (LCD) ) Displayed on 35 or stored in the external memory 36. The camera control CPU 34 reads image data stored in the external memory 36 and displays it on the liquid crystal display device 35.

  When the operation unit 40 such as a shutter release switch or a zooming switch is operated, a signal corresponding to the operation is input to the camera control CPU 34, and each unit is controlled based on the signal input by the camera control CPU 34. For example, when the shutter release switch is operated, a command signal is sent from the camera control CPU 34 to the timing control unit 37, the light beam taken in via the zoom lens 21 is input to the image sensor 31, and the timing control unit 37. Thus, the signal readout timing of the image sensor 31 is controlled.

  Signals related to the control of the zoom lens 21, for example, an AF (Auto Focus) signal, an AE (Auto Exposure) signal, a zooming signal, and the like are sent from the camera control CPU 34 to the lens control unit 38, and the lens control unit 38 performs zoom drive unit 22. The focus driving unit 23 and the iris driving unit 25 are controlled, and the zoom lens 21 is changed to a predetermined state.

  The imaging apparatus 10 is provided with a camera shake sensor 39 that detects camera shake caused by vibrations of the image sensor 31. When the camera shake sensor 39 detects camera shake, the detection signal is input to the camera control CPU 34, and the camera A correction signal is generated by the control CPU 34, and the correction signal is sent to the shift lens driving unit 24 of the camera unit 20 via the lens control unit 38. When the correction signal is input to the shift lens driving unit 24, the shift lens is moved by the shift lens driving unit 24 in a direction that cancels the displacement of the image in the image sensor 31 due to camera shake based on the input correction signal.

  It should be noted that the shapes and numerical values of the respective parts shown in the above-described embodiments are merely examples of embodiments for carrying out the present invention, and the technical scope of the present invention is interpreted in a limited manner by these. There should be no things.

FIGS. 2 to 15 show the best mode for carrying out the imaging apparatus and the zoom lens according to the present invention, and FIG. 8 is a diagram showing the refractive power arrangement of the zoom lens according to the first embodiment. It is a figure which shows the lens structure of 1st Embodiment of this invention zoom lens. FIG. 4 and FIG. 5 show aberration diagrams of numerical examples in which specific numerical values are applied to the first embodiment, and this drawing shows spherical aberration, astigmatism, distortion aberration, and lateral aberration in the wide-angle end state. FIG. It is a figure which shows the spherical aberration, the astigmatism, the distortion aberration, and the lateral aberration in the intermediate focal length state. It is a figure which shows the spherical aberration, astigmatism, distortion aberration, and lateral aberration in a telephoto end state. It is a figure which shows the lens structure of 2nd Embodiment of this invention zoom lens. FIG. 8 and FIG. 9 show aberration diagrams of numerical examples in which specific numerical values are applied to the second embodiment, and this figure shows spherical aberration, astigmatism, distortion aberration, and lateral aberration in the wide-angle end state. FIG. It is a figure which shows the spherical aberration, the astigmatism, the distortion aberration, and the lateral aberration in the intermediate focal length state. It is a figure which shows the spherical aberration, astigmatism, distortion aberration, and lateral aberration in a telephoto end state. It is a figure which shows refractive power arrangement | positioning of the zoom lens of 3rd Embodiment. It is a figure which shows the lens structure of 3rd Embodiment of this invention zoom lens. FIG. 13 and FIG. 14 show aberration diagrams of numerical examples in which specific numerical values are applied to the third embodiment, and this drawing shows spherical aberration, astigmatism, distortion aberration, and lateral aberration in the wide-angle end state. FIG. It is a figure which shows the spherical aberration, the astigmatism, the distortion aberration, and the lateral aberration in the intermediate focal length state. It is a figure which shows the spherical aberration, astigmatism, distortion aberration, and lateral aberration in a telephoto end state. It is a block diagram which shows one Embodiment of this invention imaging device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Zoom lens, 2 ... Zoom lens, 3 ... Zoom lens, G1 ... 1st lens group, G2 ... 2nd lens group, G3 ... 3rd lens group, G4 ... 4th lens group, G5 ... 5th lens group, L21 ... negative lens, L22 ... negative lens, L23 ... positive lens, L24 ... negative lens, L31 ... positive lens, L32 ... positive lens, L33 ... negative lens, 10 ... imaging device, 21 ... zoom lens, 31 ... imaging device

Claims (7)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power, which are arranged in order from the object side to the image side. 4 lens groups, the first lens group and the third lens group are fixed in the optical axis direction, and the second lens group is arranged at the time of zooming between the wide-angle end state and the telephoto end state. A zoom lens in which the fourth lens group moves in the optical axis direction so as to compensate for a change in image plane position accompanying movement in the optical axis direction of the second lens group while moving in the optical axis direction,
An aperture stop is disposed adjacent to the object side of the third lens group;
The third lens group includes a positive lens having a convex surface facing the object side, and a cemented negative lens formed by cementing a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side. It is arranged in order from the image side,
A zoom lens characterized by satisfying the following conditional expressions (1) and (2):
(1) 6 <| f3b | / fw <10
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state f1: focal length of the first lens group ft: focal length in the telephoto end state The zoom lens according to claim 1, wherein the following conditional expression (3) is satisfied.
(3) 4 <f3 / fw
However,
f3: The focal length of the third lens group. The zoom lens according to claim 2, wherein the following conditional expression (4) is satisfied.
(4) 4 <r3a / fw <5
However,
r3a: The radius of curvature of the object side lens surface of the positive lens disposed closest to the image side in the third lens group. The zoom lens according to claim 3, wherein the following conditional expression (5) is satisfied.
(5) 0.3 <| f2 | / (fw · ft) ^1/2 <0.39
However,
f2: The focal length of the second lens group. The second lens group includes a meniscus first negative lens having a concave surface facing the image side, a biconcave second negative lens, a positive lens having a convex surface facing the object side, and a third surface having a concave surface facing the image side. The zoom lens according to any one of claims 1 to 4, wherein the negative lens is arranged in order from the object side to the image side. The zoom lens according to claim 5, wherein a cemented lens is configured by cementing a positive lens and a third negative lens of the second lens group. An imaging apparatus comprising a zoom lens and an image sensor that converts an optical image formed by the zoom lens into an electrical signal,
The zoom lens is
A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power, which are arranged in order from the object side to the image side. 4 lens groups,
The first lens group and the third lens group are fixed in the optical axis direction;
During zooming between the wide-angle end state and the telephoto end state, the second lens group moves in the optical axis direction, and the image plane position varies with the movement of the second lens group in the optical axis direction. The fourth lens group is moved in the optical axis direction so as to compensate,
An aperture stop is disposed adjacent to the object side of the third lens group;
The third lens group includes a positive lens having a convex surface facing the object side, and a cemented negative lens formed by cementing a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side. It is arranged in order from the image side,
An imaging apparatus that satisfies the following conditional expression (1) and conditional expression (2):
(1) 6 <| f3b | / fw <10
(2) 1.8 <f1 / (fw · ft) ^1/2 <2.2
However,
f3b: focal length of the cemented negative lens constituting the third lens group fw: focal length in the wide-angle end state f1: focal length of the first lens group ft: focal length in the telephoto end state

Images