JP5928428B2 - Variable magnification optical system, imaging optical device, and digital equipment - Google Patents

Description

  The present invention relates to a variable magnification optical system, an imaging optical device, and a digital device. For example, a compact zooming optical system suitable for an interchangeable lens digital camera that captures a subject image with an image sensor, and imaging optical that outputs the subject image captured with the zoom optical system and the image sensor as an electrical signal The present invention relates to a device and a digital device with an image input function such as a digital camera equipped with the imaging optical device.

  In a conventional variable magnification optical system used as an interchangeable lens for a single-lens reflex camera, for example, a positive / negative positive / positive type as described in Patent Document 1 or a positive / negative positive / negative type as described in Patent Document 2, It has become the mainstream zoom type. In recent years, the compactness of a mirrorless lens interchangeable camera in which a flip-up mirror is removed from a single-lens reflex camera has been accepted by users, and its market is expanding. Among such mirrorless lens interchangeable cameras, there are cameras that cannot use phase difference AF (autofocus), which has been mainstream in conventional single-lens reflex cameras. In such a camera, so-called contrast AF is used in which focusing is performed by scanning the focusing lens group to find a place where the contrast is maximized.

  The problem is the weight of the focusing lens group. In the case of phase difference AF, the amount of movement of the focusing lens group necessary for focusing can be calculated using information from the AF sensor, and therefore the focusing lens group can be moved according to the amount. On the other hand, in the case of contrast AF, the information obtained from the AF sensor is only the instantaneous contrast value. By moving the focusing lens group and reading the change in contrast at that time, the place where the contrast becomes maximum is searched. The focusing operation will be performed. Therefore, when the amount of movement of the focusing lens group that moves before focusing is compared between contrast AF and phase difference AF, the former case is overwhelmingly large.

  In view of the above, in a variable power optical system that intends to support contrast AF, the weight reduction of the focusing lens group is a major point. In this regard, in the lens systems described in Patent Documents 1 and 2, the focusing lens group cannot be said to be sufficiently light, and a new optical solution is required to be created.

JP 2009-271471 A JP 2011-221422 A

  In the lens systems described in Patent Documents 1 and 2, when it is attempted to reduce the weight of the focusing lens group, it is considered to perform focusing with the lens group located on the image side of the third group having a smaller lens diameter. It is done. However, in the lens system described in Patent Document 2, since the fourth group plays a role of an anti-vibration function, if the focusing mechanism is arranged in the vicinity of the fourth group, the focusing drive mechanism and the anti-vibration drive mechanism In this case, there is a concern in terms of space efficiency.

  Conventionally, only a relatively telephoto lens has been equipped with an anti-vibration function, but as the zoom lens increases in magnification, it has been installed in the zoom lens. The zoom lens is also being installed. There are imaging apparatuses that perform image stabilization by moving the image sensor in a plane perpendicular to the optical axis, and the image stabilization function is becoming a semi-standard function.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a high-performance variable-power optical system having an anti-vibration function while the focusing lens group is lightweight and the overall size of the optical system is compact. It is an object to provide a system, an imaging optical apparatus and a digital apparatus including the system.

In order to achieve the above object, a variable magnification optical system according to a first aspect of the present invention includes, in order from the object side, a first group having positive power, a second group having negative power, and a third group having positive power. a fourth group having positive power, a fifth and a group made, the variable magnification optical system for performing zooming by varying the axial spacing of each group having a negative power,
Focusing is performed by moving the fourth group on the optical axis,
Anti-vibration is performed by moving a sub-group including the most image-side lens in the second group in a plane substantially perpendicular to the optical axis,
The following conditional expressions (1) and (2a) are satisfied.
M / N <0.5 (1)
4.0 <fv / f2 <10.0 (2a)
However,
M: number of lenses constituting the sub group,
N: the number of lenses constituting the second group,
It is assumed that multiple cemented lenses are handled ,
fv: focal length of sub-group,
f2: focal length of the second group,
Der Ru.

The variable magnification optical system according to the second aspect of the invention includes, in order from the object side, a first group having positive power, a second group having negative power, a third group having positive power, and a fourth group having positive power. A variable power optical system that includes a fifth group having negative power and a sixth group having positive power, and performs zooming by changing an on-axis interval of each group,
Focusing is performed by moving the fourth group on the optical axis,
Anti-vibration is performed by moving a sub-group including the most image-side lens in the second group in a plane substantially perpendicular to the optical axis,
The following conditional expressions (1) and (2 a ) are satisfied.
M / N <0.5 (1)
4.0 <fv / f2 < 10.0 ... ( 2a )
However,
M: number of lenses constituting the sub group,
N: the number of lenses constituting the second group,
It is assumed that multiple cemented lenses are handled,
fv: focal length of sub-group,
f2: focal length of the second group,
It is.

A variable magnification optical system according to a third aspect of the invention is characterized in that, in the first or second aspect of the invention, the following conditional expression (3) is satisfied.
−4.0 <(rA + rB) / (rA−rB) <− 0.7 (3)
However,
rA: radius of curvature of the most object-side surface of the subgroup,
rB: radius of curvature of the most image side surface of the subgroup,
It is.

  A variable magnification optical system according to a fourth invention is characterized in that, in any one of the first to third inventions, an aspheric surface is disposed closer to the object side than the sub group in the second group. To do.

  A variable magnification optical system according to a fifth invention is characterized in that, in the fourth invention, the lens including the aspheric surface is only one biconvex positive lens.

A variable magnification optical system according to a sixth aspect of the present invention is the optical system according to any one of the first to fifth aspects, wherein the sub group includes a single negative lens, and satisfies the following conditional expression (4): It is characterized by.
ft / Ymax <7.5 (4)
However,
ft: focal length of the entire system at the telephoto end,
Ymax: an ideal image height that does not include distortion, with the maximum image height, where f is the focal length of the entire system, and ω is the half angle of view, ω = tan ⁻¹ (Ymax / f) It is.

A variable magnification optical system according to a seventh aspect of the invention is characterized in that, in the sixth aspect, the following conditional expression (5) is satisfied.
60 <Vd (5)
However,
Vd: Abbe number of the negative lens constituting the sub group,
It is.

  A variable magnification optical system according to an eighth invention is characterized in that, in any one of the first to fifth inventions, the sub group comprises a cemented lens in which a negative lens and a positive lens are cemented.

  According to a ninth aspect of the present invention, in the zoom optical system according to any one of the first to eighth aspects, the third group and the fifth group move together at the time of zooming.

  A zooming optical system according to a tenth aspect of the present invention is the optical system according to any one of the first to ninth aspects, wherein the zooming unit moves the third group and the fourth group for focusing at the time of zooming. The fifth group moves together.

A variable magnification optical system according to an eleventh aspect of the invention is characterized in that, in any one of the first to tenth aspects of the invention, the following conditional expression (6) is satisfied.
−4.0 <f5 / f3 <−0.8 (6)
However,
f3: focal length of the third group,
f5: focal length of the fifth group,
It is.

A variable magnification optical system according to a twelfth aspect of the invention is characterized in that, in any one of the first to eleventh aspects of the invention, the following conditional expression (7) is satisfied.
−1.0 <M5 / f5 <−0.1 (7)
However,
M5: distance on the optical axis from the fifth group position at the wide-angle end to the fifth group position at the telephoto end,
f5: focal length of the fifth group,
It is.

A variable magnification optical system according to a thirteenth invention is characterized in that, in any one of the first to twelfth inventions, the following conditional expression (8) is satisfied.
1.0 <f4 / f3 <4.0 (8)
However,
f3: focal length of the third group,
f4: focal length of the fourth group,
It is.

A variable magnification optical system according to a fourteenth invention is characterized in that, in any one of the first to thirteenth inventions, the following conditional expression (9) is satisfied.
0.5 <M4 / M5 <1.5 (9)
However,
M4: distance on the optical axis from the fourth group position at the wide-angle end to the fourth group position at the telephoto end,
M5: distance on the optical axis from the fifth group position at the wide-angle end to the fifth group position at the telephoto end,
It is.

  An image pickup optical apparatus according to a fifteenth aspect of the present invention is a zoom optical system according to any one of the first to fourteenth aspects of the present invention, an image pickup element that converts an optical image formed on the light receiving surface into an electrical signal, and , And the zooming optical system is provided so that an optical image of a subject is formed on the light receiving surface of the image sensor.

  According to a sixteenth aspect of the present invention, there is provided a digital apparatus including the imaging optical device according to the fifteenth aspect, to which at least one function of still image shooting and moving image shooting of a subject is added.

  According to the present invention, it is possible to realize a high-performance variable magnification optical system and imaging optical device having a vibration-proof function while the focusing lens group is lightweight and the size of the entire optical system is compact. By using the variable magnification optical system or the imaging optical device for a digital device (for example, a digital camera), a high-performance image input function can be added to the digital device in a compact manner.

The optical block diagram of 1st Embodiment (Example 1). The optical block diagram of 2nd Embodiment (Example 2). The optical block diagram of 3rd Embodiment (Example 3). FIG. 3 is a longitudinal aberration diagram of Example 1. FIG. 6 is a longitudinal aberration diagram of Example 2. FIG. 6 is a longitudinal aberration diagram of Example 3. FIG. 6 is a lateral aberration diagram at the wide-angle end before and after camera shake correction in Example 1. FIG. 4 is a lateral aberration diagram before and after camera shake correction in Example 1 at the telephoto end. FIG. 6 is a lateral aberration diagram at the wide-angle end before and after camera shake correction in Example 2. FIG. 6 is a lateral aberration diagram before and after camera shake correction in Example 2 at the telephoto end. FIG. 10 is a lateral aberration diagram at the wide-angle end before and after camera shake correction in Example 3. FIG. 10 is a lateral aberration diagram before and after camera shake correction in Example 3 at the telephoto end. The schematic diagram which shows the example of schematic structure of the digital apparatus carrying a variable magnification optical system.

  Hereinafter, a variable magnification optical system, an imaging optical device, and a digital apparatus according to the present invention will be described. The zoom optical system according to the present invention includes, in order from the object side, a first group having positive power, a second group having negative power, a third group having positive power, and a fourth group having positive power. A variable power optical system including a fifth group having negative power (power: an amount defined by the reciprocal of the focal length), and performing zooming by changing an axial interval of each group, Focusing is performed by moving the fourth group on the optical axis, and the sub group including the lens closest to the image side in the second group is moved in a plane substantially perpendicular to the optical axis to prevent vibration ( That is, the camera shake correction) is performed.

  In the power arrangement including the five groups of positive, negative, positive, positive and negative in order from the object side as described above, when the anti-vibration lens group is arranged in the second group, a driving mechanism for driving the fourth group which is the focusing lens group, and the anti-vibration Since the driving mechanism for driving the sub group which is the lens group is greatly separated, there is an advantage that the layout efficiency in the lens barrel is increased. It is conceivable to use the entire second lens group as an anti-vibration lens group, but since the second lens group has a large lens diameter and a relatively large weight, the anti-vibration lens group operates at a speed that can handle the frequency of camera shake. If it is going to make it, the drive mechanism which has a big drive force will be needed, and the enlargement of the whole system will be caused.

  In a variable magnification optical system including five groups of positive, negative, positive, and negative in order from the object side, the variable magnification action due to the change in the 1-2 group interval and the 2-3 group interval plays a major part in the variable magnification action of the entire optical system. Yes. Therefore, in order to reduce the size of the zoom optical system, it is effective to increase the optical power of the second group. In this case, it is necessary to dispose a relatively strong negative lens in the second lens group. However, if such a lens is decentered for vibration isolation, a large decentering aberration is generated and the vibration is prevented. It is difficult to ensure the performance of Generally, when a plurality of lens groups are in a relationship that cancels each other by generating aberrations with different signs (that is, a strong relationship in terms of aberration coupling), one of these lens groups is decentered. As a result, a large decentration aberration is generated.

  From the above viewpoint, when a part of the lens group is used as an anti-vibration lens group, the sub-lens group located in the center of the lens group is anti-vibrated to be a fixed group, an anti-vibration group, a fixed group Rather than dividing the lens group into three groups, it is better to divide the outer sub-lens group in contact with the lens group interval into two groups, such as an anti-vibration group and a fixed group, without increasing the number of lenses. This is advantageous in increasing the independence of aberrations of the sub lens group.

  In a variable magnification optical system including five positive, negative, positive, positive, and negative groups in order from the object side, the off-axis light beam at the wide-angle end is allowed to pass, so the lens diameter on the most object side in the second group is relatively large. Therefore, it is desirable in terms of weight to use the image side sub lens group in the second group as the image stabilization lens group instead of using the object side sub lens group in the second group as the image stabilization lens group. In addition, since there is a space generated by the difference in lens diameter between the object side and the image side in the second group outside the lens diameter on the image side in the second group, an anti-vibration drive mechanism is disposed in this space. Is also advantageous in terms of space efficiency.

In addition, it is desirable to satisfy the following conditional expression (1) in order to reduce the weight of the image stabilizing lens group.
M / N <0.5 (1)
However,
M: number of lenses constituting the sub group,
N: the number of lenses constituting the second group,
Therefore, a plurality of cemented lenses are handled.

  If the number M of lenses in the sub group increases and falls outside the range of the conditional expression (1), the weight of the anti-vibration lens group increases, so that it is necessary to increase the driving force of the driving mechanism, leading to an increase in size of the actuator. As a result, the entire system becomes larger. Since the second group is the group having the strongest power in the variable magnification optical system, the number N of constituent lenses of the second group is a point that determines the size of the entire system. For this reason, if the number N of constituent lenses of the second group becomes small and falls outside the range of the conditional expression (1), it is difficult to correct aberrations (particularly astigmatism) if a strong power is to be maintained. Decreasing the power will lead to an increase in the size of the entire system. Therefore, by satisfying the conditional expression (1), it is possible to achieve a reduction in size and high performance of the variable magnification optical system having the image stabilization function in a balanced manner.

  According to the above characteristic configuration, it is possible to realize a high-performance variable magnification optical system and imaging optical device having a vibration isolation function while the focusing lens group is lightweight and the entire size of the optical system is compact. If a miniaturized variable magnification optical system or imaging optical device having the image stabilization function is used in a digital device such as a digital camera, it becomes possible to add a high-performance image input function to the digital device in a compact manner. It can contribute to the downsizing, cost reduction, high performance and high functionality of digital equipment. For example, since the variable power optical system according to the present invention is suitable as an interchangeable lens for a mirrorless type interchangeable lens digital camera, it is possible to realize a lightweight and compact interchangeable lens that is convenient to carry. The conditions for achieving such effects in a well-balanced manner and achieving higher optical performance, downsizing, etc. will be described below.

It is desirable to satisfy the following conditional expression (2).
3.0 <fv / f2 <12.0 (2)
However,
fv: focal length of sub-group,
f2: focal length of the second group,
It is.

  If the lower limit of conditional expression (2) is not reached, the power of the image stabilizing lens group becomes too strong, and it becomes difficult to suppress the occurrence of aberration in the image stabilizing lens group alone. For example, spherical aberration and astigmatism increase. As the spherical aberration increases, the decentration coma aberration that occurs when the decentering is performed for image stabilization increases. When the astigmatism increases, the inclination of the image plane (so-called half-blurring aberration) that occurs when the lens is decentered for image stabilization increases. On the other hand, if the upper limit of conditional expression (2) is exceeded, the power of the image stabilization lens group becomes too weak, making it difficult to ensure the necessary image stabilization sensitivity, or moving the image stabilization lens group. It is necessary to increase the distance, and the variable magnification optical system becomes large. Furthermore, the amount of astigmatism variation during zooming may increase due to an increase in the power of the entire second group, for example. Therefore, by satisfying the conditional expression (2), it is possible to achieve a reduction in size and high performance of the variable magnification optical system having an anti-vibration function in a balanced manner.

It is more desirable to satisfy the following conditional expression (2a).
4.0 <fv / f2 <10.0 (2a)
This conditional expression (2a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (2). Therefore, the above effect can be further increased preferably by satisfying conditional expression (2a).

It is desirable to satisfy the following conditional expression (3).
−4.0 <(rA + rB) / (rA−rB) <− 0.7 (3)
However,
rA: radius of curvature of the most object-side surface of the subgroup,
rB: radius of curvature of the most image side surface of the subgroup,
It is.

  Arranging the negative lens having the strongest power in the second group on the most object side in the second group is effective in reducing the lens diameter of the second group. In this case, the convergent light that has passed through the positive first group is changed to a divergent light beam by a negative lens having a strong negative power located on the most object side in the second group, and the ray height is increased in the second group. It will proceed to the image side while gradually raising it. If the upper limit of conditional expression (3) is exceeded, spherical aberration occurring on the front and rear surfaces of the image stabilizing lens group (that is, the sub group) will increase, making it difficult to suppress the occurrence of spherical aberration in the image stabilizing lens group alone. . As a result, the decentration coma aberration generated when the image stabilizing lens group is decentered increases, and it becomes difficult to ensure optical performance during image stabilization. On the other hand, if the lower limit of conditional expression (3) is not reached, it is advantageous in terms of suppressing spherical aberration generated by the vibration-proof lens group alone, but securing the optical power required by the vibration-proof lens group alone. Becomes difficult. Therefore, by satisfying the conditional expression (3), it is possible to achieve a reduction in size and high performance of the variable magnification optical system having the image stabilization function in a balanced manner.

It is more desirable to satisfy the following conditional expression (3a).
−3.0 <(rA + rB) / (rA−rB) <− 0.9 (3a)
This conditional expression (3a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (3). Therefore, the above effect can be further increased preferably by satisfying conditional expression (3a).

  In the second group, it is desirable that an aspherical surface be disposed closer to the object side than the sub group. When the amount of aberration generated by the vibration-proof lens group alone in the second group is suppressed to be sufficiently small, the aberration amount of the other fixed group (that is, the portion closer to the object side than the sub group in the second group) is also sufficiently small. If not suppressed, a large amount of aberration is generated in the entire second lens group, and it becomes difficult to suppress performance change during zooming. As described above, in order to reduce the size of the variable magnification optical system, it is necessary to increase the optical power of the second group. Therefore, in order not to increase the number of lenses in the second group, It is effective to arrange an aspherical surface.

  In the fixed group in the second group, it is desirable to dispose a biconvex positive lens so that aberrations generated by a strong negative lens can be canceled. Further, it is desirable that the aspherical surface is disposed only on the biconvex positive lens from the viewpoint of ease of molding of the aspherical lens, that is, from the viewpoint of cost. Accordingly, it is preferable that the lens including the aspheric surface is only one biconvex positive lens.

It is desirable that the sub group includes one negative lens and satisfies the following conditional expression (4).
ft / Ymax <7.5 (4)
However,
ft: focal length of the entire system at the telephoto end,
Ymax: an ideal image height that does not include distortion, with the maximum image height, where f is the focal length of the entire system, and ω is the half angle of view, ω = tan ⁻¹ (Ymax / f) It is.

  It is desirable to configure the anti-vibration lens group with a single negative lens in order to reduce the weight for reducing the anti-vibration driving load. At this time, if the upper limit of conditional expression (4) is exceeded, the lateral chromatic aberration generated by the anti-vibration lens group at the time of decentering becomes too large compared to the maximum image height, and optical performance at the time of image stabilization is ensured. Becomes difficult.

It is desirable to satisfy the following conditional expression (5).
60 <Vd (5)
However,
Vd: Abbe number of the negative lens constituting the sub group,
It is.

  When the anti-vibration lens group is composed of one negative lens, it is desirable to satisfy the conditional expression (5). If the lower limit of conditional expression (5) is not reached, lateral chromatic aberration that occurs during image stabilization increases, making it difficult to ensure optical performance during image stabilization.

  The sub group is preferably composed of a cemented lens in which a negative lens and a positive lens are cemented. By using a cemented lens made up of a negative lens and a positive lens as an anti-vibration lens group, it is possible to reduce the occurrence of lateral chromatic aberration when the anti-vibration lens group is decentered. In addition, it is possible to suppress the deterioration of aberration caused by the relative position error between the negative lens and the positive lens, which occurs during manufacturing, as compared with the case where they are configured separately.

  It is desirable that the third group and the fifth group move together when zooming. By adopting a configuration in which the third group and the fifth group move together during zooming, the third group and the fifth group can be placed on a single moving means. Therefore, with such a configuration, it is possible to reduce manufacturing error factors and reduce performance degradation due to manufacturing errors.

  It is desirable that the third group, the driving means for moving the fourth group for focusing, and the fifth group move together during zooming, and the driving means moves the third group and the fourth group together. It is further desirable that the axial distance between the fourth group and the axial distance between the fourth group and the fifth group change. By adopting a configuration in which the third group, the fourth group driving means, and the fifth group move together at the time of zooming, the third group, the fourth group moving means, and the fifth group are placed on a single moving group. Is possible. In such a configuration, in a lens system equipped with a purely mechanical so-called manual zoom, depending on the focus state, the focusing lens group and the adjacent lens group can collide by a sudden zooming operation by the user. There is sex. For this reason, it is necessary to take measures to prevent the lens system from being destroyed even if it collides. On the other hand, in the configuration in which the third group, the fourth group moving means, and the fifth group are mounted on a single moving group as described above, the fourth group does not collide with the third group or the fifth group in any focusing state. Can be guaranteed completely. Therefore, it is not necessary to take the above measures, and the mechanism can be simplified.

It is desirable to satisfy the following conditional expression (6).
−4.0 <f5 / f3 <−0.8 (6)
However,
f3: focal length of the third group,
f5: focal length of the fifth group,
It is.

  If the lower limit of conditional expression (6) is not reached, the relative power of the fifth group with respect to the third group becomes too weak, and the zooming effect due to the movement of the fifth group becomes insufficient. On the other hand, if the upper limit of conditional expression (6) is exceeded, the relative power of the fifth group with respect to the third group becomes too strong, and the back principal point position of the entire optical system at the wide-angle end is brought closer to the image plane. It becomes difficult to obtain the desired wide-angle end focal length. Even if it is difficult to secure the focal length at the wide-angle end even if the zooming action is insufficient, the entire zooming optical system will not be able to correct aberrations, resulting in an overall increase in residual aberrations and optical performance. Will deteriorate. Therefore, by satisfying conditional expression (6), it is possible to achieve, in a balanced manner, miniaturization and high performance of the variable magnification optical system having the image stabilization function.

It is more desirable to satisfy the following conditional expression (6a).
−2.0 <f5 / f3 <−1.0 (6a)
The conditional expression (6a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (6). Therefore, the above effect can be further enhanced preferably by satisfying conditional expression (6a).

It is desirable to satisfy the following conditional expression (7).
−1.0 <M5 / f5 <−0.1 (7)
However,
M5: distance on the optical axis from the fifth group position at the wide-angle end to the fifth group position at the telephoto end,
f5: focal length of the fifth group,
It is.

  If the lower limit of conditional expression (7) is not reached, the power of the fifth group becomes too strong, or the amount of movement of the fifth group becomes too large, and astigmatism and coma change due to the movement of the fifth group. It becomes difficult to suppress. On the contrary, if the upper limit of conditional expression (7) is exceeded, the moving amount of the fifth group becomes too small, or the power of the fifth group becomes too weak, so that the zooming action by the fifth group becomes insufficient. . As a result, in order to obtain the desired zooming, it is necessary to increase the zooming action between the first and second groups, and the total length of the optical system at the telephoto end increases, or the second group tries to avoid it. As the power increases, it becomes difficult to suppress fluctuations in astigmatism and coma during zooming. Therefore, by satisfying the conditional expression (7), it is possible to achieve a reduction in size and high performance of the variable magnification optical system having an anti-vibration function in a balanced manner.

It is more desirable to satisfy the following conditional expression (7a).
−0.7 <M5 / f5 <−0.2 (7a)
This conditional expression (7a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (7). Therefore, the above effect can be further increased preferably by satisfying conditional expression (7a).

It is desirable to satisfy the following conditional expression (8).
1.0 <f4 / f3 <4.0 (8)
However,
f3: focal length of the third group,
f4: focal length of the fourth group,
It is.

  If the lower limit of conditional expression (8) is not reached, the relative power of the fourth group with respect to the third group becomes too strong, making it difficult to suppress fluctuations in astigmatism accompanying the movement of the fourth group during focusing. Become. On the other hand, if the upper limit of conditional expression (8) is exceeded, most of the convergence effect of the optical system will be assigned to the third group, and the spherical aberration and coma generated in the third group will increase. Therefore, by satisfying the conditional expression (8), it is possible to achieve a reduction in size and high performance of the variable magnification optical system having the image stabilization function in a balanced manner.

It is more desirable to satisfy the following conditional expression (8a).
1.1 <f4 / f3 <3.0 (8a)
This conditional expression (8a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (8). Therefore, the above effect can be further increased preferably by satisfying conditional expression (8a).

It is desirable to satisfy the following conditional expression (9).
0.5 <M4 / M5 <1.5 (9)
However,
M4: distance on the optical axis from the fourth group position at the wide-angle end to the fourth group position at the telephoto end,
M5: distance on the optical axis from the fifth group position at the wide-angle end to the fifth group position at the telephoto end,
It is.

  If the lower limit of conditional expression (9) is not reached, the amount of movement of the fourth group relative to the amount of movement of the fifth group is relatively small, and the amount of movement of the fifth group necessary to obtain the desired zooming action is reduced. In order to ensure, it is necessary to ensure a large 4-5 group spacing at the wide-angle end. As a result, the position of the rear principal point of the entire optical system moves away from the image plane, making it difficult to obtain a desired wide-angle end focal length. On the other hand, if the upper limit of conditional expression (9) is exceeded, the amount of movement of the fourth group relative to the amount of movement of the fifth group is relatively large, and 3-5 at the wide-angle end in order to secure the focus movement amount. It is necessary to ensure a large group interval. As a result, the optical system becomes large. Alternatively, if it is attempted to avoid this, it is necessary to increase the power of the fourth group, and it becomes difficult to suppress fluctuations in astigmatism accompanying the movement of the fourth group during focusing. Therefore, by satisfying conditional expression (9), it is possible to achieve a reduction in size and performance of the variable magnification optical system having the image stabilization function in a well-balanced manner.

It is more desirable to satisfy the following conditional expression (9a).
0.6 <M4 / M5 <1.2 (9a)
This conditional expression (9a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (9). Therefore, the above effect can be further increased preferably by satisfying conditional expression (9a).

  The zoom optical system according to the present invention is suitable for use as an imaging lens for a digital device with an image input function (for example, a digital camera). By combining this with an imaging device or the like, an image of a subject is optically displayed. It is possible to configure an image pickup optical device that takes in and outputs as an electrical signal. The imaging optical device is an optical device that constitutes a main component of a camera used for still image shooting and moving image shooting of a subject. For example, a variable power optical system that forms an optical image of an object in order from the object (that is, subject) side. (For example, a zoom lens) and an image sensor that converts an optical image formed by the zoom optical system into an electrical signal. In addition, the variable magnification optical system having the above-described characteristic configuration is arranged so that the optical image of the subject is formed on the light receiving surface (that is, the imaging surface) of the image sensor, thereby achieving high performance at a small size and low cost. It is possible to realize an imaging optical device having the above and a digital device including the same.

  Examples of digital devices with an image input function include cameras such as digital cameras, video cameras, surveillance cameras, in-vehicle cameras, and videophone cameras. It can also be built in or externally attached to personal computers, portable digital devices (for example, mobile phones, smart phones (high performance mobile phones), mobile computers, etc.), peripheral devices (scanners, printers, etc.), and other digital devices. One with a camera function can be mentioned. As can be seen from these examples, it is possible not only to configure a camera by using an imaging optical device, but also to add a camera function by mounting the imaging optical device on various devices. For example, a digital device with an image input function such as a mobile phone with a camera can be configured.

  FIG. 13 is a schematic cross-sectional view showing a schematic configuration example of a digital device DU as an example of a digital device with an image input function. The imaging optical device LU mounted on the digital device DU shown in FIG. 13 sequentially forms a zoom lens ZL (AX: light) that forms an optical image (image plane) IM of the object so as to be variable in order from the object (namely, subject) side. Axis), a plane parallel plate PT (cover glass of the image sensor SR; corresponding to an optical filter such as an optical low-pass filter and an infrared cut filter arranged as necessary), and a light receiving surface by a zoom lens ZL (Imaging surface) An imaging element SR that converts an optical image IM formed on the SS into an electrical signal is provided. When a digital device DU with an image input function is constituted by this imaging optical device LU, the imaging optical device LU is usually arranged inside the body, but when necessary to realize the camera function, a form as necessary is adopted. Is possible. For example, the unitized imaging optical device LU can be configured to be detachable or rotatable with respect to the main body of the digital device DU.

  The zoom lens ZL is a variable power optical system that includes five groups of positive, negative, positive, positive and negative, and performs zooming by changing the on-axis interval of each group, and the fourth group is moved along the optical axis AX. The sub-group including the lens closest to the image side in the second group is moved in a plane substantially perpendicular to the optical axis AX so as to perform image stabilization. Further, at the time of zooming, at least the third group, the fourth group, and the fifth group move relative to the image plane IM, and form an optical image IM on the light receiving surface SS of the image sensor SR. .

  As the image sensor SR, for example, a solid-state image sensor such as a CCD (Charge Coupled Device) type image sensor having a plurality of pixels or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor is used. Since the zoom lens ZL is provided so that the optical image IM of the subject is formed on the light receiving surface SS which is a photoelectric conversion unit of the image sensor SR, the optical image IM formed by the zoom lens ZL is the image sensor. It is converted into an electric signal by SR.

  The digital device DU includes a signal processing unit 1, a control unit 2, a memory 3, an operation unit 4, a display unit 5 and the like in addition to the imaging optical device LU. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, and the like in the signal processing unit 1 as necessary, and recorded as a digital video signal in the memory 3 (semiconductor memory, optical disc, etc.) In some cases, it is transmitted to other devices via a cable or converted into an infrared signal or the like (for example, a communication function of a mobile phone). The control unit 2 is composed of a microcomputer and controls functions such as shooting functions (still image shooting function, moving image shooting function, etc.) and image reproduction functions; control of a lens moving mechanism for zooming, focusing, camera shake correction, etc. Do it intensively. For example, the control unit 2 controls the imaging optical device LU so as to perform at least one of still image shooting and moving image shooting of a subject. The display unit 5 includes a display such as a liquid crystal monitor, and performs image display using an image signal converted by the image sensor SR or image information recorded in the memory 3. The operation unit 4 is a part including operation members such as an operation button (for example, a release button) and an operation dial (for example, a shooting mode dial), and transmits information input by the operator to the control unit 2.

  Here, the specific optical configuration of the zoom lens ZL will be described in more detail with reference to the first to third embodiments. FIGS. 1 to 3 are optical configuration diagrams corresponding to the zoom lenses ZL constituting the first to third embodiments, respectively, at a wide angle end (W), an intermediate focal length state (M), and a telephoto end (T ) Shows the lens arrangement, optical path, etc. in the optical section.

  In the first to third embodiments (FIGS. 1 to 3), in order from the object side, the first group Gr1 having positive power, the second group Gr2 having negative power, and the third group having positive power. It includes Gr3, a fourth group Gr4 having positive power, and a fifth group Gr5 having negative power, and is configured to perform zooming (that is, zooming) by changing the interval between the groups. At the time of zooming, at least the third group Gr3, the fourth group Gr4, and the fifth group Gr5 move relative to the image plane IM. The aperture stop ST is located on the object side of the third group Gr3, and moves together with the third group Gr3 during zooming. At the time of focusing, the fourth group Gr4 moves along the optical axis AX. That is, the fourth group Gr4 is a focusing lens group, and moves to the object side during focusing on a short-distance object, as indicated by an arrow mF. The sub group GrV including the most image side lens in the second group Gr2 is an anti-vibration lens group. As shown by an arrow mV, camera shake correction is performed by moving perpendicularly to the optical axis AX.

  The first embodiment (FIG. 1) of the zoom lens ZL has a zoom configuration in which all groups are movable at the time of zooming in five groups of positive, negative, positive and negative. However, the third group Gr3 and the fifth group Gr5 are linked so as to move together. In zooming from the wide-angle end (W) to the telephoto end (T), the first group Gr1 moves monotonously to the object side, the second group Gr2 moves to the object side, and then moves to the image side. Further, the third group Gr3 to the fifth group Gr5 move monotonously toward the object side.

  The second embodiment (FIG. 2) of the zoom lens ZL has a zoom configuration in which all groups are movable at the time of zooming in five groups of positive, negative, positive and negative. However, the third group Gr3 and the fifth group Gr5 are linked so as to move together. In zooming from the wide-angle end (W) to the telephoto end (T), the first group Gr1 monotonously moves to the object side, the second group Gr2 moves to the image side, and then moves to the object side, and then again the image. Move to the side. The third group Gr3 to the fifth group Gr5 move to the object side and move to the image side slightly before the telephoto end (T).

  The third embodiment (FIG. 3) of the zoom lens ZL has a zoom configuration in which the first group Gr1 to the fifth group Gr5 are movable during zooming with six groups of positive, negative, positive, positive and negative. However, the third group Gr3 and the fifth group Gr5 are linked so as to move together. In zooming from the wide-angle end (W) to the telephoto end (T), the first group Gr1 moves monotonously to the object side, the second group Gr2 moves to the object side, then moves to the image side, and again moves to the object side. Move to the side. Further, the third group Gr3 to the fifth group Gr5 move monotonously toward the object side.

  Each group in the first embodiment (FIG. 1) is configured as follows in order from the object side when each lens is viewed with a paraxial surface shape. The first group Gr1 includes a cemented lens including a negative meniscus lens concave on the image side and a positive meniscus lens convex on the object side, and a positive meniscus lens convex on the object side. The second group Gr2 includes a negative meniscus lens that is concave on the image side, a biconcave negative lens, a biconvex positive lens that includes a double-sided aspheric surface, a cemented lens that includes a biconcave negative lens and a planoconvex positive lens. (Subgroup GrV). The third lens unit Gr3 includes a biconvex positive lens composed of a double-sided aspheric surface, and a cemented lens composed of a biconcave negative lens and a biconvex positive lens. ST is arranged. The fourth group Gr4 is composed of one biconvex positive lens composed of aspherical surfaces on both sides. The fifth group Gr5 is composed of a single cemented lens composed of a biconcave negative lens and a positive meniscus lens convex on the object side.

  Each group in the second embodiment (FIG. 2) is configured as follows in order from the object side when each lens is viewed with a paraxial surface shape. The first group Gr1 includes a cemented lens including a negative meniscus lens concave on the image side and a positive meniscus lens convex on the object side, and a positive meniscus lens convex on the object side. The second group Gr2 includes a negative meniscus lens concave on the image side, a biconcave negative lens, a biconvex positive lens composed of a double-sided aspheric surface, and a negative meniscus lens (sub group GrV) concave on the object side. It consists of The third lens unit Gr3 includes a biconvex positive lens composed of a double-sided aspheric surface, and a cemented lens composed of a biconcave negative lens and a biconvex positive lens. ST is arranged. The fourth group Gr4 is composed of a single positive meniscus lens convex on the image side made of double-sided aspherical surfaces. The fifth group Gr5 is composed of one biconcave negative lens.

  Each group in the third embodiment (FIG. 3) is configured as follows in order from the object side when each lens is viewed with a paraxial surface shape. The first group Gr1 includes a cemented lens including a negative meniscus lens concave on the image side and a positive meniscus lens convex on the object side, and a positive meniscus lens convex on the object side. The second group Gr2 includes two negative meniscus lenses concave on the image side, a biconvex positive lens composed of a double-sided aspheric surface, and a cemented lens composed of a biconcave negative lens and a planoconvex positive lens (sub group GrV). And is composed of. The third lens unit Gr3 includes a biconvex positive lens composed of a double-sided aspheric surface, and a cemented lens composed of a biconcave negative lens and a biconvex positive lens. ST is arranged. The fourth group Gr4 is composed of one biconvex positive lens composed of aspherical surfaces on both sides. The fifth group Gr5 is composed of a single cemented lens composed of a biconcave negative lens and a positive meniscus lens convex on the object side. The sixth group Gr6 is composed of one biconvex positive lens.

  Hereinafter, the configuration and the like of the zoom optical system embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 to 3 (EX1 to 3) listed here are numerical examples corresponding to the first to third embodiments, respectively, and are optical configuration diagrams showing the first to third embodiments. (FIGS. 1 to 3) show the lens configurations, optical paths, and the like of the corresponding first to third embodiments.

In the construction data of each embodiment, as surface data, in order from the left column, the surface number, the radius of curvature r (mm), the axial upper surface distance d (mm), and the refractive indexes nd and d regarding the d-line (wavelength 587.56 nm). The Abbe number vd for the line is shown. A surface with * in the surface number is an aspheric surface, and the surface shape is defined by the following expression (AS) using a local orthogonal coordinate system (x, y, z) with the surface vertex as the origin. . As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each example is 0, and E−n = × 10 ⁻ⁿ for all data.
z = (c · h ² ) / [1 + √ {1− (1 + K) · c ² · h ² }] + Σ (Aj · h ^j ) (AS)
However,
h: height in the direction perpendicular to the z axis (optical axis AX) (h ² = x ² + y ² ),
z: the amount of sag in the direction of the optical axis AX at the position of the height h (based on the surface vertex),
c: curvature at the surface vertex (the reciprocal of the radius of curvature r),
K: conic constant,
Aj: j-order aspheric coefficient,
It is.

  As various data, the zoom ratio (magnification ratio) is shown, and for each focal length state W, M, T, the focal length (f, mm), F number (FNO), half angle of view (ω, °) of the entire system. ), Image height (mm), total lens length (TL, mm), back focus (BF, mm), and variable surface distance di (i: surface number, mm). The focal length (f1, f2, f3, f4, f5, f6; mm) is shown. However, the back focus BF used here is the distance from the image side surface of the plane parallel plate PT to the image plane IM, and the total lens length TL is the distance from the lens front surface to the image plane IM. Table 1 shows data related to the conditional expression for each example, and Table 2 shows values corresponding to the conditional expression for each example.

  FIGS. 4 to 6 are aberration diagrams corresponding to Example 1 to Example 3 (EX1 to EX3) (normal time (before decentering), longitudinal aberration diagram in the infinite focus state), and wide angle end ( (W), intermediate (M), and various aberrations at the telephoto end (T) (in order from the left are spherical aberration, astigmatism, and distortion aberration). 4 to 6, FNO is the F number, and Y ′ (mm) is the maximum image height (corresponding to the distance from the optical axis AX) on the light receiving surface SS of the image sensor SR. In the spherical aberration diagram, solid line d, alternate long and short dash line g, and alternate long and two short dashes line c represent spherical aberration (mm) with respect to d line, g line, and c line, respectively, and broken line SC represents unsatisfactory sine condition (mm). Yes. In the astigmatism diagram, the broken line DM is the meridional image plane, and the solid line DS is the sagittal image plane, and represents each astigmatism (mm) with respect to the d-line. In the distortion diagram, the solid line represents the distortion (%) with respect to the d-line.

  7 to 12 are lateral aberration diagrams of the first to third embodiments (EX1 to EX3) in the infinite focus state before the eccentricity (normal time) and after the eccentricity (when the camera shake is corrected). 8 correspond to the first embodiment, FIGS. 9 and 10 correspond to the second embodiment, and FIGS. 11 and 12 correspond to the third embodiment, respectively. 7 to 12, (A) and (B) are lateral aberration diagrams before decentering, and (C) to (E) are lateral aberration diagrams after decentering (y ′ (mm) is the image sensor SR. Is the image height on the light receiving surface SS (corresponding to the distance from the optical axis AX). 7, 9, and 11, the axis when the image blur at an angle of 0.3 degrees at the wide angle end (W) is corrected by the eccentricity of the decentering lens component (that is, the sub group (anti-vibration lens group) GrV). 8, 10, and 12, when the image blur at an angle of 0.3 degrees is corrected by the eccentricity of the decentering lens component in FIGS. 8, 10, and 12. This represents the deterioration of lateral aberration on and off the axis.

Example 1
Unit: mm
Surface data Surface number rd nd vd
1 48.898 1.800 1.84666 23.78
2 32.654 6.169 1.49700 81.61
3 272.082 0.300
4 32.035 4.572 1.69680 55.48
5 109.041 Variable
6 269.010 1.200 1.91082 35.25
7 9.488 5.286
8 -219.618 0.800 1.77250 49.65
9 25.498 0.504
10 * 23.223 2.903 1.84666 23.78
11 * -80.599 1.000
12 -46.624 0.800 1.83481 42.72
13 33.992 1.609 1.84666 23.78
14 ∞ variable
15 (Aperture) ∞ 0.930
16 * 10.618 3.818 1.73077 40.50
17 * -82.008 1.817
18 -89.945 1.057 1.90366 31.31
19 7.459 4.867 1.49700 81.61
20 -24.493 Variable
21 * 30.345 2.867 1.58313 59.38
22 * -51.375 variable
23 -72.731 1.000 1.83481 42.72
24 20.048 1.834 1.67270 32.17
25 73.090 Variable
26 ∞ 4.200 1.51680 64.20
27 ∞ BF

Aspheric data
K A4 A6 A8
10th surface 0.00000 -2.26008E-06 -1.12461E-07 -7.12245E-09
11th surface 0.00000 -4.13799E-05 -1.90824E-07 -8.43392E-09
16th surface 0.00000 -3.83814E-05 -1.45574E-08 4.00546E-09
17th surface 0.00000 3.32806E-05 3.50436E-07 2.45802E-09
21st surface 0.00000 -8.40535E-05 -2.14381E-06
22nd face 0.00000 -8.48713E-05 -2.02828E-06

Various data Zoom ratio 7.143
Wide angle (W) Medium (M) Telephoto (T)
Focal length 14.000 37.422 100.000
F number 3.600 5.000 5.700
Half angle of view 37.686 16.119 6.173
Image height 9.704 10.854 10.984
Total lens length 95.044 104.622 115.000
BF 1.076 1.054 0.991
d5 1.324 12.639 24.576
d14 21.043 8.844 1.970
d20 7.911 6.367 8.513
d22 2.802 4.346 2.200
d25 11.554 22.038 27.417

Zoom lens group data Group Start focal length
1 1 49.663
2 6 -10.103
3 15 22.659
4 21 33.143
5 23 -34.395

Example 2
Unit: mm
Surface data Surface number rd nd vd
1 46.831 1.800 1.84666 23.78
2 31.030 5.572 1.49700 81.61
3 179.398 0.300
4 27.841 4.571 1.69680 55.48
5 87.175 Variable
6 156.065 1.200 1.91082 35.25
7 9.247 5.536
8 -39.150 0.800 1.77250 49.65
9 23.322 0.501
10 * 22.052 2.974 1.84666 23.78
11 * -42.991 1.000
12 -35.026 0.800 1.49700 81.61
13 -152.535 Variable
14 (Aperture) ∞ 0.930
15 * 10.953 2.612 1.73077 40.50
16 * -76.558 1.646
17 -324.973 1.001 1.90366 31.31
18 7.913 4.597 1.49700 81.61
19 -21.398 Variable
20 * -65.511 2.648 1.58313 59.38
21 * -18.281 variable
22 -30.571 1.000 1.83481 42.72
23 1223.683 Variable
24 ∞ 4.200 1.51680 64.20
25 ∞ BF

Aspheric data
K A4 A6 A8
10th surface 0.00000 3.46391E-06 1.77182E-07 -1.29219E-08
11th surface 0.00000 -2.40172E-05 1.56016E-07 -1.33631E-08
15th surface 0.00000 -3.55272E-05 -1.25475E-07 1.16889E-08
16th surface 0.00000 4.25279E-05 2.18514E-07 6.64296E-09
20th surface 0.00000 -1.55759E-04 -3.96523E-06
21st surface 0.00000 -1.06996E-04 -2.97413E-06

Various data Zoom ratio 5.000
Wide angle (W) Medium (M) Telephoto (T)
Focal length 14.000 31.300 70.000
F number 3.600 5.000 5.700
Half angle of view 37.686 19.061 8.783
Image height 9.696 10.765 10.980
Total lens length 87.458 91.726 100.000
BF 1.076 1.055 0.991
d5 1.272 6.723 20.278
d13 19.335 6.960 1.970
d19 8.004 6.147 7.344
d21 2.803 4.660 3.463
d23 11.281 22.494 22.266

Zoom lens group data Group Start focal length
1 1 47.089
2 6 -10.516
3 14 20.050
4 20 42.604
5 22 -35.715

Example 3
Unit: mm
Surface data Surface number rd nd vd
1 49.692 1.800 1.84666 23.78
2 33.275 6.163 1.49700 81.61
3 338.133 0.300
4 33.430 4.469 1.69680 55.48
5 121.392 Variable
6 900.526 1.200 1.91082 35.25
7 9.533 4.966
8 376.111 0.800 1.77250 49.65
9 28.891 0.602
10 * 28.693 2.799 1.84666 23.78
11 * -64.608 1.000
12 -39.469 0.800 1.83481 42.72
13 26.388 1.835 1.84666 23.78
14 ∞ variable
15 (Aperture) ∞ 0.930
16 * 10.722 3.391 1.73077 40.50
17 * -91.497 2.011
18 -107.198 1.143 1.90366 31.31
19 7.485 4.661 1.49700 81.61
20 -31.084 Variable
21 * 33.824 2.923 1.58313 59.38
22 * -45.302 variable
23 -68.702 1.000 1.80420 46.49
24 61.291 1.094 1.78472 25.72
25 75.683 Variable
26 7769.088 1.159 1.83481 42.72
27 -331.545 11.250
28 ∞ 4.200 1.51680 64.20
29 ∞ BF

Aspheric data
K A4 A6 A8
10th surface 0.00000 9.15770E-07 -2.01406E-07 -4.84394E-09
11th surface 0.00000 -5.00636E-05 -3.22182E-07 -6.52489E-09
16th surface 0.00000 -3.91008E-05 -2.99751E-08 2.32568E-09
17th surface 0.00000 2.48704E-05 2.47912E-07 1.66315E-09
21st face 0.00000 -7.22289E-05 -1.94517E-06
22nd face 0.00000 -6.45725E-05 -1.84095E-06

Various data Zoom ratio 7.143
Wide angle (W) Medium (M) Telephoto (T)
Focal length 14.000 37.420 100.000
F number 3.600 5.003 5.700
Half angle of view 37.686 16.120 6.173
Statue height 9.699 10.857 10.980
Total lens length 96.397 110.203 120.000
BF 1.076 1.056 0.991
d5 1.416 12.773 24.705
d14 20.604 9.508 1.970
d20 8.209 8.158 9.517
d22 3.680 3.732 2.373
d25 0.916 14.482 19.948

Zoom lens group data Group Start focal length
1 1 49.772
2 6 -10.075
3 15 24.045
4 21 33.667
5 23 -44.370
6 26 380.920

DU Digital equipment LU Imaging optical device ZL Zoom lens (variable magnification optical system)
Gr1 first group Gr2 second group Gr3 third group Gr4 fourth group Gr5 fifth group Gr6 sixth group GrV sub group (anti-vibration lens group)
ST stop (aperture stop)
SR Image sensor SS Light receiving surface
IM image plane (optical image)
AX Optical axis 1 Signal processing unit 2 Control unit 3 Memory 4 Operation unit 5 Display unit

Claims (16)

In order from the object side, a first group having positive power, a second group having negative power, a third group having positive power, a fourth group having positive power, and a fifth group having negative power, A variable power optical system that performs variable power by changing the on-axis spacing of each group,
Focusing is performed by moving the fourth group on the optical axis,
Anti-vibration is performed by moving a sub-group including the most image-side lens in the second group in a plane substantially perpendicular to the optical axis,
A zoom optical system characterized by satisfying the following conditional expressions (1) and (2a) :
M / N <0.5 (1)
4.0 <fv / f2 <10.0 (2a)
However,
M: number of lenses constituting the sub group,
N: the number of lenses constituting the second group,
It is assumed that multiple cemented lenses are handled ,
fv: focal length of sub-group,
f2: focal length of the second group,
Der Ru. In order from the object side, a first group having positive power, a second group having negative power, a third group having positive power, a fourth group having positive power, and a fifth group having negative power, A sixth variable lens unit having positive power, and a variable power optical system that performs variable power by changing the axial interval of each lens group,
Focusing is performed by moving the fourth group on the optical axis,
Anti-vibration is performed by moving a sub-group including the most image-side lens in the second group in a plane substantially perpendicular to the optical axis,
The following conditional expressions (1) and (2 a) variable magnification optical system you characterized by satisfying the;
M / N <0.5 (1)
4.0 <fv / f2 < 10.0 ... ( 2a )
However,
M: number of lenses constituting the sub group,
N: the number of lenses constituting the second group,
It is assumed that multiple cemented lenses are handled,
fv: focal length of sub-group,
f2: focal length of the second group,
It is. The zoom lens system according to claim 1 or 2, wherein the following conditional expression (3) is satisfied:
−4.0 <(rA + rB) / (rA−rB) <− 0.7 (3)
However,
rA: radius of curvature of the most object-side surface of the subgroup,
rB: radius of curvature of the most image side surface of the subgroup,
It is.   4. The variable magnification optical system according to claim 1, wherein an aspherical surface is disposed closer to the object side than the sub group in the second group. 5.   5. The variable magnification optical system according to claim 4, wherein the lens including the aspherical surface is only one biconvex positive lens. The variable power optical system according to any one of claims 1 to 5, wherein the sub group includes one negative lens, and satisfies the following conditional expression (4):
ft / Ymax <7.5 (4)
However,
ft: focal length of the entire system at the telephoto end,
Ymax: an ideal image height that does not include distortion, with the maximum image height, where f is the focal length of the entire system, and ω is the half angle of view, ω = tan ⁻¹ (Ymax / f) It is. The zoom optical system according to claim 6, wherein the following conditional expression (5) is satisfied:
60 <Vd (5)
However,
Vd: Abbe number of the negative lens constituting the sub group,
It is.   6. The variable magnification optical system according to claim 1, wherein the sub group includes a cemented lens in which a negative lens and a positive lens are cemented.   The zoom optical system according to any one of claims 1 to 8, wherein the third group and the fifth group move together during zooming.   The zoom lens according to any one of claims 1 to 9, wherein the third group, the driving unit that moves the fourth group for focusing, and the fifth group move together during zooming. The zoom optical system according to item. The zoom lens system according to any one of claims 1 to 10, wherein the following conditional expression (6) is satisfied:
−4.0 <f5 / f3 <−0.8 (6)
However,
f3: focal length of the third group,
f5: focal length of the fifth group,
It is. The zoom lens system according to claim 1, wherein the following conditional expression (7) is satisfied:
−1.0 <M5 / f5 <−0.1 (7)
However,
M5: distance on the optical axis from the fifth group position at the wide-angle end to the fifth group position at the telephoto end,
f5: focal length of the fifth group,
It is. The zoom lens system according to claim 1, wherein the following conditional expression (8) is satisfied:
1.0 <f4 / f3 <4.0 (8)
However,
f3: focal length of the third group,
f4: focal length of the fourth group,
It is. The zoom lens system according to claim 1, wherein the following conditional expression (9) is satisfied:
0.5 <M4 / M5 <1.5 (9)
However,
M4: distance on the optical axis from the fourth group position at the wide-angle end to the fourth group position at the telephoto end,
M5: distance on the optical axis from the fifth group position at the wide-angle end to the fifth group position at the telephoto end,
It is.   A variable power optical system according to any one of claims 1 to 14, and an image sensor that converts an optical image formed on the light receiving surface into an electrical signal, the light receiving surface of the image sensor An imaging optical apparatus, wherein the zoom optical system is provided so that an optical image of a subject is formed.   16. A digital apparatus comprising the imaging optical device according to claim 15 to which at least one function of still image shooting and moving image shooting of a subject is added.

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