JP2020071237A - Zoom lens and image capturing device - Google Patents

Abstract

To provide a zoom lens which is reduced in weight and allows for employing a lens barrel structure with superior dustproof and splashproof properties, and to provide an image capturing device.SOLUTION: In order to clear the above problem, a zoom lens is provided, substantially consisting of a positive first lens group G1, negative second lens group G2, positive third lens group G3, and succeeding lens group arranged in order from the object side, the zoom lens being configured such that, when zooming from the wide-angle end to the telephoto end, the first lens group G1 is stationary relative to an image plane and at least the second and third lens groups G2, G3 move along an optical axis to change distances between adjacent lens groups along the optical axis. The zoom lens satisfies predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens and an image pickup apparatus, and particularly to a zoom lens and an image pickup apparatus suitable for a small-sized image pickup apparatus using a solid-state image pickup element or the like.

  2. Description of the Related Art In recent years, image capturing apparatuses using solid-state image pickup devices such as digital still cameras and digital video cameras have become widespread. As an imaging optical system of an imaging device, for example, a plurality of lens groups are provided, and the focal length is changed by changing the distance between the lens groups during zooming, and some lens groups are used as focusing groups on the optical axis. There is known a zoom lens that focuses on a subject by moving the.

  Since the focal length of the zoom lens can be adjusted according to the distance to the subject, it is highly convenient at the time of image pickup and the demand from the user is high. With the rapid progress of high performance and downsizing of image pickup devices in recent years, there is a strong demand for high performance and downsizing of zoom lenses.

  By the way, in order to realize a high-performance zoom lens, it is necessary to satisfactorily correct various aberrations in the entire zoom range. However, if the number of lenses is increased to correct aberrations, the zoom lens becomes larger. Therefore, in order to reduce the size of the zoom lens, it is necessary to configure the zoom lens with a small number of lenses.

  In order to satisfactorily correct various aberrations over the entire zoom range, it is necessary to suppress variations in various aberrations during zooming. In order to suppress the variation of various aberrations, it is effective to move the first lens group arranged closest to the object side as the focusing group on the optical axis to focus on the subject. However, the first lens group is composed of lenses having a relatively large diameter. Therefore, as the first lens group moves, the center of gravity of the zoom lens moves during focusing, which may cause image blur.

  Furthermore, in order to move the first lens group, it is necessary to configure the lens barrel into a nested structure and to extend the inner cylinder or outer cylinder with respect to the outer cylinder or inner cylinder. Therefore, when the first lens group is the focusing group, it is difficult to provide the lens barrel of the zoom lens with the dustproof and dripproof structure. The zoom lens is an image pickup optical system such as an image pickup device that can be carried by a user such as a single-lens reflex camera, and an image pickup device that is installed and fixed on various moving bodies such as an on-vehicle image pickup device and a surveillance camera or a building. Is also used as. An image pickup device installed and fixed on various moving bodies or structures is often used outdoors, and thus is required to have a dustproof and dripproof structure.

  Therefore, in the zoom lens disclosed in Patent Document 1, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, the third lens group having a positive refractive power, and the negative refractive power are arranged in this order. A fourth lens unit having a positive power and a fifth lens unit having a positive refractive power are provided, and the first lens unit is fixed to the image plane during zooming and focusing, and the fourth lens unit serves as a focusing unit. As a result, it is possible to employ a lens barrel structure that is excellent in dustproof and dripproof while suppressing the variation of the position of the center of gravity during focusing.

  Also, in the zoom lens disclosed in Patent Document 2, in order from the object side, the first lens group having a positive refractive power, the second lens group having a negative refractive power, the third lens group having a positive refractive power, and the negative lens group A fourth lens group having a refractive power and a fifth lens group having a positive refractive power are provided, and the first lens group is fixed to the image plane during zooming and focusing, and the fourth lens group is a focusing group. Is being done.

JP, 2016-139125, A Japanese Patent No. 4794912

  However, in the zoom lens disclosed in Patent Document 1, a lens made of a glass material having a refractive index of 1.80432 for the d-line is arranged on the most object side of the second lens group. It is effective to use a lens made of a glass material having such a high refractive index in order to improve the performance and size of the zoom lens. However, a glass material having a high refractive index tends to have a large specific gravity. Further, the lens arranged on the object side of the zoom lens tends to have a larger diameter than the lens arranged on the image side. Therefore, like the zoom lens disclosed in Patent Document 1, when a lens made of a glass material having a high refractive index and a large specific gravity is arranged on the most object side of the second lens group, the zoom lens becomes heavy, and thus the weight of the zoom lens is reduced. Becomes difficult. Further, when a lens made of a glass material having a large specific gravity is arranged on the object side of the zoom lens, the center of gravity of the zoom lens is located on the object side. Therefore, it is difficult to keep the zoom lens horizontal.

  Also in the zoom lens disclosed in Patent Document 2, the first lens group is composed of a lens made of a glass material having a high refractive index and a large specific gravity. Therefore, like the zoom lens disclosed in Patent Document 1, it is difficult to reduce the weight of the zoom lens, and the position of the center of gravity is on the object side.

  An object of the present invention is to provide a zoom lens and an image pickup apparatus which can adopt a lens barrel structure excellent in dustproof and dripproof, and which is downsized and lightweight.

In order to solve the above problems, a 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, and a positive refractive power arranged in order from the object side. The third lens unit having a power and the succeeding lens unit are substantially formed, and the first lens unit is fixed to the image plane at the time of zooming from the wide-angle end to the telephoto end and is adjacent to each other. At least the second lens group and the third lens group move in the optical axis direction so that the distance between them on the optical axis changes, and the following conditional expression is satisfied.
(1) 7.8 <L / y × Nd2ave <11
(2) 8.0 <L / y × Nd2max <13
However,
L: Optical total length of the zoom lens y: Maximum image height of the zoom lens Nd2ave: Average refractive index of the negative lens included in the second lens group with respect to d line Nd2max: Negative lens included in the second lens group Refractive index for d-line of negative lens made of glass material with the highest refractive index for d-line

  Further, in order to solve the above-mentioned problems, the image pickup apparatus according to the present invention is provided with an image pickup element for converting an optical image formed by the zoom lens into an electric signal on the image side of the zoom lens. To do.

  According to the present invention, it is possible to provide a zoom lens and an image pickup device which can adopt a lens barrel structure excellent in dustproof and dripproof, and which is downsized and lightweight.

FIG. 4 is a lens cross-sectional view of a zoom lens according to a first exemplary embodiment of the present invention when focused on an object at infinity, in which an upper part shows a lens cross section at a telephoto end, a middle part shows an intermediate focal length position, and a lower part shows a lens cross section at a wide-angle end. FIG. 7 is an aberration diagram at the time of wide-angle end of the zoom lens in Example 1 when focused on infinity. FIG. 6 is an aberration diagram for focusing on infinity at an intermediate focal length position of the zoom lens in Example 1; FIG. 4 is an aberration diagram at the telephoto end of the zoom lens in Example 1 when focused on infinity. FIG. 6 is a lens cross-sectional view of a zoom lens according to a second exemplary embodiment of the present invention when focused on an object at infinity, in which an upper part shows a lens cross section at a telephoto end, a middle part shows an intermediate focal length position, and a lower part shows a lens cross section at a wide-angle end. FIG. 8 is an aberration diagram at the time of wide-angle end focusing on infinity of the zoom lens in Example 2; FIG. 7 is an aberration diagram at infinity focusing at an intermediate focal length position of the zoom lens in Example 2; FIG. 8 is an aberration diagram at the telephoto end of the zoom lens in Example 2 when focused on infinity. FIG. 6 is a lens cross-sectional view of a zoom lens according to a third exemplary embodiment of the present invention when focused on infinity, in which an upper part shows a lens cross section at a telephoto end, a middle part shows an intermediate focal length position, and a lower part shows a lens cross section at a wide-angle end. FIG. 9 is an aberration diagram at the time of wide-angle end of the zoom lens in Example 3 when focused on infinity. FIG. 16 is an aberration diagram at the time of focusing at infinity at the intermediate focal length position of the zoom lens in Example 3; FIG. 8 is an aberration diagram at the telephoto end of the zoom lens in Example 3 when focused on infinity. FIG. 8 is a lens cross-sectional view of a zoom lens of Example 4 of the present invention when focused on an object at infinity, in which an upper part shows a lens cross section at a telephoto end, a middle part shows an intermediate focal length position, and a lower part shows a lens cross section at a wide-angle end. FIG. 16 is an aberration diagram at the time of wide angle end of the zoom lens in Example 4 when focused on infinity. FIG. 13 is an aberration diagram at infinity focusing at the intermediate focal length position of the zoom lens in Example 4; FIG. 16 is an aberration diagram at the telephoto end of the zoom lens in Example 4 when focused on infinity.

  Embodiments of a zoom lens and an image pickup apparatus according to the present invention will be described below. However, the zoom lens and the imaging device described below are one mode of the zoom lens and the imaging device according to the present invention, and the zoom lens and the imaging device according to the present invention are not limited to the following modes.

1. Zoom lens 1-1. Optical Configuration of Zoom Lens A zoom lens according to the present invention has a first lens group having a positive refracting power, a second lens group having a negative refracting power, and a positive refracting power which are arranged in order from the object side. It is substantially composed of a third lens group that has and a subsequent lens group. Here, “substantially constituted” means that among the lens groups constituting the zoom lens, the lens groups having substantial power are the first lens group, the second lens group, the third lens group, and It means that it is permissible to include a lens group having substantially no power but an optical element other than the lens, such as a diaphragm and a cover glass, which is a subsequent lens group. Each lens group includes at least one lens.

  The zoom lens adopts a telephoto power arrangement in which the first lens group has a converging effect and the second lens group arranged on the object side has a diverging effect. Therefore, at the telephoto end, the total optical length can be shortened compared to the focal length, so that the zoom lens can be downsized while achieving a narrow angle of view. Hereinafter, the optical configuration of each lens group will be described in more detail.

(1) First Lens Group The first lens group includes at least one positive lens, and the specific lens configuration is not particularly limited as long as it has a positive refracting power as a whole. For example, the first lens group may be composed of one positive lens, or may be composed of a plurality of positive lenses. However, in order to reduce the size and weight of the zoom lens, it is preferable that the number of lenses forming the first lens group is small. The first lens group is preferably composed of three or less lens components, more preferably two or less lens components, more preferably one lens component, and one positive lens ( Most preferably, it is composed of a single lens made of one glass material having a positive refractive power. Here, the lens component means a single lens made of one glass material or a cemented lens in which lenses made of different glass materials are cemented, and one lens component does not include an air gap. A so-called compound aspherical lens is also included in the single lens component (hereinafter the same). Further, in order to favorably correct distortion, it is more preferable that the most object side surface of the first lens group be a convex surface.

  In the zoom lens, since the first lens group is fixed to the image surface during zooming and focusing, a mechanism for moving the first lens group is unnecessary. Therefore, the length of the lens barrel can be fixed, and the lens barrel can be easily provided with a dustproof and dripproof structure.

  In the zoom lens, the first lens group is composed of a lens having a larger diameter than other lens groups. Therefore, when the specific gravity of the lenses forming the first lens group becomes too large, the first lens group becomes heavy, and the center of gravity of the zoom lens is likely to be located on the object side. Therefore, from this viewpoint, the specific gravity of the glass material of the lenses forming the first lens group should not be too large. On the other hand, in order to obtain a zoom lens having a small telephoto ratio (optical total length of the zoom lens / focal length of the zoom lens) at the telephoto end, it is preferable to dispose a strong positive refractive power in the first lens group. Therefore, it is preferable that the glass material of the positive lens forming the first lens group has a high refractive index. However, as described above, a glass material having a high refractive index tends to have a large specific gravity. Therefore, from this viewpoint, it is not preferable that the specific gravity of the glass material of the lenses constituting the first lens group becomes too small. From these facts, in order to obtain a compact and lightweight zoom lens with high optical performance while suppressing the center of gravity of the zoom lens from being located on the object side, the refraction of the glass material of the positive lens that constitutes the first lens group is required. The rate is preferably 1.70 or less and 1.45 or more, and preferably 1.68 or less and 1.48 or more.

  The fact that the center of gravity of the zoom lens is located on the object side means that the center of gravity is located at a position within a distance of ⅓ × L from the surface of the zoom lens located closest to the object. To do. However, “L” means the total optical length of the zoom lens.

(2) Second Lens Group The second lens group includes at least one negative lens, and its specific lens configuration is not particularly limited as long as it has a negative refracting power as a whole. For example, the second lens group may be composed of one negative lens, or may be composed of a plurality of negative lenses. In order to obtain a zoom lens having a smaller telephoto ratio, it is preferable to dispose a strong negative refractive power in the second lens group. At this time, by configuring the second lens group with two or more negative lenses, it is possible to prevent the curvature of each surface from becoming too small, and to suppress the occurrence of field curvature in the second lens group. Further, by making the second lens group include at least one positive lens, it is possible to suppress the occurrence of chromatic aberration in the second lens group. It is preferable to configure the second lens group with four or less lens components in order to reduce the weight of the zoom lens. In order to further reduce the weight of the second lens group, it is more preferable that the second lens group be composed of three or less lens components.

  In the zoom lens, the second lens group moves along the optical axis during zooming. Therefore, when the specific gravity of the second lens group is large, the position of the center of gravity of the zoom lens is likely to change depending on the position of the second lens group during zooming. In particular, the lens located closest to the object side in the second lens group has a relatively large diameter. Therefore, for the same reason as described in the first lens group, it is preferable that the refractive index of the glass material of the lens disposed closest to the object side in the second lens group is 1.70 or less and 1.45 or more, It is preferably 1.68 or less and 1.48 or more. Further, it is preferable that the following conditional expressions (1) and (2) are satisfied.

(3) Third Lens Group The third lens group includes at least one positive lens, and the specific lens configuration is not particularly limited as long as it has a positive refracting power as a whole. For example, a configuration including at least one negative lens is preferable because the occurrence of chromatic aberration can be suppressed.

(4) Subsequent Lens Group In the zoom lens, the subsequent lens group refers to all the lens groups arranged on the image side of the third lens group and closer to the object side than the image surface and having substantial power. The subsequent lens group may be composed of one lens group or may be composed of two or more lens groups. When the subsequent lens group includes two or more lens groups, it is possible to suppress aberration variation during zooming, and it becomes easier to achieve high optical performance in the entire zooming range. In addition, when the number of lens groups forming the subsequent lens group increases, it becomes easy to suppress the center of gravity of the zoom lens from being located on the object side. However, if the number of lens groups forming the subsequent lens group increases, it is difficult to reduce the size and weight of the zoom lens. From these viewpoints, the number of lens groups forming the subsequent lens group is preferably 3 or less, and more preferably 2 or less. For example, it is preferable that the subsequent lens group includes, in order from the object side, a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power. By adopting this configuration, it is possible to suppress aberration fluctuations in spherical aberration, astigmatism, axial chromatic aberration, and chromatic aberration of magnification that occur in subsequent lens groups during zooming, and to achieve high optical performance over the entire zoom range. Easy to realize.

  It is preferable that the lens group arranged closest to the image side of the succeeding lens group is composed of one lens component. With this configuration, the number of lens components is reduced, and the zoom lens can be made smaller and lighter. It is more preferable that the lens group disposed closest to the image side of the subsequent lens group is composed of a single lens.

1-2. Operation (1) Operation during zooming In the zoom lens, zooming is performed by changing the interval on the optical axis between the lens groups adjacent to each other when zooming. The presence / absence of movement of each lens group during zooming, the direction of movement, the amount of movement, and the like are preferably set as follows, for example.

i) First lens group At the time of zooming from the wide-angle end to the telephoto end, it is preferable that the first lens group be fixed with respect to the image plane. By making the first lens group a fixed group, as described above, it becomes easy to make the lens barrel have a dustproof and dripproof structure.

ii) Second lens group In the zoom lens, it is preferable to move the second lens group in the optical axis direction during zooming from the wide-angle end to the telephoto end. At this time, it is more preferable to move the second lens group to the image side.

iii) Third lens group In the zoom lens, it is preferable to move the third lens group in the optical axis direction at the time of zooming from the wide-angle end to the telephoto end. At this time, it is more preferable to move the third lens group to the object side.

iv) Subsequent lens group The following lens group may be fixed to the optical axis at the time of zooming or moved on the optical axis and may include one or more lens groups having a refractive power. The group may include a plurality of lens groups, and the distance on the optical axis between the lens groups adjacent to each other may be changed during zooming. When the subsequent lens group is composed of one lens group, that one lens group may be a fixed group that is fixed to the image plane during zooming, or a movable group that moves in the optical axis direction. May be. When the succeeding lens group is composed of one lens group, if that one lens group is made to be a fixed group, the optical total length does not change in the entire zoom range, so it is better to make the lens barrel dust-proof and drip-proof structure. It will be easier. If one of the lens groups is a moving group, it becomes easy to suppress aberration variation during zooming, and it becomes easier to realize a zoom lens having high optical performance over the entire zoom range.

  When the succeeding lens group is composed of two or more lens groups, the lens group arranged closest to the image plane side is a fixed group fixed to the image plane during zooming. It is preferable for adopting a drip-proof structure. The reason is the same as above.

  When the subsequent lens group is composed of two or more lens groups, the lens group (that is, the fourth lens group) disposed adjacent to the image side of the third lens group moves in the optical axis direction during zooming. It is preferable that it is a moving group. By using the fourth lens group as a moving group, it becomes easier to suppress aberration variation during zooming, and it is possible to realize a zoom lens having higher optical performance in the entire zooming range.

  When the succeeding lens group is composed of, for example, two lens groups, that is, a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power, the fourth lens group is used as a moving group and It is preferable that the lens group is a fixed group. With this configuration, it is possible to achieve high optical performance in the entire zoom range and to easily adopt the dust-proof and drip-proof structure of the lens barrel.

  When the subsequent lens group is composed of three lens groups, the fourth lens group may be a fixed group or the fourth lens group may be a movable group. By using the fourth lens group as a moving group and moving the fourth lens group and the fifth lens group on the optical axis by different amounts of movement, respectively, it is possible to suppress aberration fluctuations at the time of zooming and achieve high optical power over the entire zoom range. Performance can be realized. Further, when the fourth lens group is a lens group having a positive refractive power and the fifth lens group is a lens group having a negative refractive power, the diameter of the fifth lens group can be reduced. At this time, by adopting the fifth lens group as the focusing group, it becomes possible to reduce the size and weight of the focusing group. Further, by making the fourth lens group a movable group and moving the fourth lens group and the sixth lens group on the optical axis with the same amount of movement during zooming, the structure of the zoom lens is simplified and the weight is reduced. You can Further, the subsequent lens group may be composed of four lens groups, and the refractive power of each lens group can be appropriately selected. At this time, it is preferable that the seventh lens group is fixed to the image plane during zooming.

  In the zoom lens, when the distance between the first lens group and the second lens group at the wide-angle end is D12w and the distance between the second lens group and the third lens group at the wide-angle end is D23w, 0.00 <D12w / D23w < It is preferable that 0.50 is satisfied in order to obtain a zoom lens having a large zoom ratio. At this time, the upper limit value is more preferably 0.40, 0.30, 0.20, or 0.10.

  In the zoom lens, when the distance between the first lens group and the second lens group at the telephoto end is D12t and the distance between the second lens group and the third lens group at the telephoto end is D23t, 0.50 <D12t / D23t Satisfying is preferable for obtaining a zoom lens having a large zoom ratio. At this time, it is more preferable that the lower limit value is any of 1.00, 1.50, 2.00, 3.00, and 5.00.

(2) Focusing operation In the zoom lens, at the time of focusing from infinity to a close object, one of the lens groups included in the following lens group is moved in the optical axis direction to obtain a subject. It is preferable to focus on. The focusing group may be any one lens group that moves on the optical axis during zooming, or may be a part of any one lens group that moves on the optical axis during zooming. .. At this time, it is preferable that the focusing group is a lens group having a negative refractive power. In the subsequent lens group, the lens group having a negative refractive power is lighter than the lens group having a positive refractive power, which is preferable in terms of reducing the weight of the focusing group. In particular, it is preferable that the focusing group is composed of one lens component having a negative refractive power. By thus forming the focusing unit from the lens component having no air gap, various mechanisms for driving the focusing unit at the time of focusing can be simplified, and the overall size and weight of the zoom lens can be reduced. Can be planned. It is more preferable to use a biconcave negative lens (single lens having negative refracting power) as the focusing group in order to improve the performance during focusing.

  Further, when the subsequent lens group is composed of a plurality of lens groups, the lens group that is arranged closest to the image side among the lens groups that configure the subsequent lens group is appropriate in adopting the dust-proof and drip-proof structure of the lens barrel. It is preferably fixed with respect to the image plane during focusing. That is, in the zoom lens, it is preferable that the lens group arranged closer to the object side than the lens group arranged closest to the image side is the focusing group. For example, when the subsequent lens group is composed of three lens groups, it is preferable that the fourth lens group or the fifth lens group be the focusing group.

  When the subsequent lens group is composed of the fourth lens group having a negative refractive power and the fifth lens group having a positive refractive power as described above, the fourth lens group at the time of focusing from infinity to a close object is used. From the above viewpoint, it is preferable to move the lens group in the optical axis direction to focus on the subject. Further, by making the fourth lens group a focusing group, it is possible to suppress aberration fluctuations due to the object distance, and even when the distance to the object is short, that is, the object image has a high resolution even during close-up imaging. Can be obtained.

(3) Operation during image stabilization Further, the zoom lens may be configured such that any one or all of the lens groups listed above are movable in a direction substantially orthogonal to the optical axis. Good. That is, any one of the lens groups listed above may be entirely or partially configured as a vibration isolation group. By providing the image stabilizing group in this way, when vibration is applied to the zoom lens and an image blur occurs, the image stabilizing group is moved in a direction substantially orthogonal to the optical axis to correct the image blur. be able to.

1-3. Conditional Expression It is preferable that the zoom lens adopts the above-described configuration and satisfies at least one conditional expression described below.

1-3-1. Conditional expression (1)
7.8 <L / y × Nd2ave <11 (1)
However,
L: total optical length of the zoom lens y: maximum image height of the zoom lens Nd2ave: average refractive index of the negative lens included in the second lens group with respect to d line

  The conditional expression (1) defines the average of the refractive indices of the negative lenses included in the second lens group with respect to the d-line with respect to the size of the zoom lens. “L / y” represents the size of the zoom lens. As described above, the specific gravity of the lens tends to increase as the refractive index of the glass material increases. By satisfying the conditional expression (1), it is possible to prevent the specific gravity of the negative lens included in the second lens group from becoming too large, and to reduce the weight of the second lens group. Therefore, it is possible to prevent the center of gravity of the zoom lens from being located on the object side.

  On the other hand, when the numerical value of the conditional expression (1) becomes less than or equal to the lower limit value, the specific gravity of the glass material of the negative lens included in the second lens group becomes small with respect to the size of the zoom lens, so that the second lens group has a small specific gravity. It is preferable in terms of weight reduction. However, in this case, since the negative lens included in the second lens group has a low refractive index, the curvature of the negative lens included in the second lens group is increased or the negative lens included in the second lens group is changed to achieve a predetermined zoom ratio. It is necessary to increase the amount of movement of the second lens group when multiplying. Increasing the curvature of the negative lens included in the second lens group is not preferable because the amount of various aberrations such as spherical aberration increases. Further, if the amount of movement of the second lens group during zooming is increased, the optical length of the zoom lens becomes longer, which is not desirable for downsizing the zoom lens.

  On the other hand, when the numerical value of the conditional expression (1) is equal to or larger than the upper limit value, the specific gravity of the glass material of the negative lens included in the second lens group becomes large with respect to the size of the zoom lens, and the weight of the second lens group is reduced. Becomes difficult. Therefore, the center of gravity of the zoom lens is likely to be located on the object side, which is not preferable.

  In order to obtain these effects, the lower limit value of conditional expression (1) is more preferably 8.0, further preferably 8.4, further preferably 8.8, and 8. It is even more preferably 88. The upper limit value of conditional expression (1) is more preferably 10.9, further preferably 10.85.

1-3-2. Conditional expression (2)
8.0 <L / y × Nd2max <13 (2)
However,
L: optical total length of the zoom lens y: maximum image height of the zoom lens Nd2max: refractive index of a negative lens made of a glass material having the highest refractive index for d line among the negative lenses included in the second lens group, for d line

  The conditional expression (2) defines the refractive index for the d line of the negative lens made of the glass material having the highest refractive index for the d line among the negative lenses included in the second lens group with respect to the size of the zoom lens. Is. “L / y” represents the size of the zoom lens. Similar to the case of the conditional expression (1), by satisfying the conditional expression (2), it is possible to prevent the specific gravity of the negative lens included in the second lens group from becoming too large, and to reduce the weight of the second lens group. be able to. Therefore, it is possible to prevent the center of gravity of the zoom lens from being located on the object side.

  On the other hand, when the numerical value of the conditional expression (2) becomes less than or equal to the lower limit value, the glass material having the highest refractive index for the d-line among the negative lenses included in the second lens group with respect to the size of the zoom lens is selected. The negative lens has a small specific gravity, which is preferable in order to reduce the weight of the second lens group. However, in this case, since the negative lens included in the second lens group has a low refractive index, the curvature of the negative lens included in the second lens group is increased or the negative lens included in the second lens group is changed to achieve a predetermined zoom ratio. It is necessary to increase the amount of movement of the second lens group when multiplying. Increasing the curvature of the negative lens included in the second lens group is not preferable because the amount of various aberrations such as spherical aberration increases. Further, if the amount of movement of the second lens group during zooming is increased, the optical length of the zoom lens becomes longer, which is not desirable for downsizing the zoom lens.

  On the other hand, when the numerical value of the conditional expression (2) is equal to or larger than the upper limit value, the specific gravity of the glass material of the negative lens included in the second lens group becomes large relative to the size of the zoom lens, and the weight of the second lens group is reduced. Becomes difficult. Therefore, the center of gravity of the zoom lens is likely to be located on the object side, which is not preferable.

  In order to obtain these effects, the lower limit value of conditional expression (2) is more preferably 8.3, further preferably 8.6, further preferably 8.8, and 8. Even more preferably, it is 9. The upper limit of conditional expression (2) is more preferably 12, and even more preferably 11.5.

1-3-3. Conditional expression (3)
0.8 <| f2 / fw | <1.4 (3)
However,
f2: focal length of the second lens group fw: focal length of the zoom lens at the wide-angle end

  The conditional expression (3) defines the ratio between the focal length of the second lens group and the focal length of the zoom lens at the wide-angle end. By satisfying conditional expression (3), it is possible to satisfactorily correct various aberrations at the time of zooming, particularly spherical aberration, image surface aberration, and coma aberration while reducing the size and weight of the zoom lens. It becomes easier to realize a zoom lens having high optical performance in the entire double range.

  On the other hand, when the numerical value of the conditional expression (3) is less than or equal to the lower limit value, the refracting power of the second lens group becomes too strong with respect to the focal length of the zoom lens at the wide angle end, resulting in spherical aberration and image surface aberration. The amount of various aberrations such as coma aberration increases, and the aberration variation during zooming increases. Therefore, in order to realize a zoom lens having high optical performance in the entire zoom range, it is necessary to increase the number of lenses for aberration correction, and it is difficult to reduce the size and weight of the zoom lens. On the other hand, when the numerical value of the conditional expression (3) is equal to or larger than the upper limit value, the refractive power of the second lens group becomes too weak with respect to the focal length of the zoom lens at the wide-angle end, so that a predetermined zoom ratio is realized. Therefore, it is necessary to increase the amount of movement of the second lens group during zooming, which increases the total optical length. Therefore, it becomes difficult to reduce the size of the zoom lens.

  In obtaining these effects, the lower limit value of conditional expression (3) is more preferably 0.9, and further preferably 1.0. The upper limit value of conditional expression (3) is more preferably 1.35.

1-3-4. Conditional expression (4)
0.75 <M2 / M3 <1.5 (4)
However,
M2: amount of movement of the second lens group during zooming from the wide-angle end to the telephoto end M3: amount of movement of the third lens group during zooming from the wide-angle end to the telephoto end

  The above conditional expression (4) is defined as the first condition at the time of zooming from the wide-angle end to the telephoto end when the second lens group and the third lens group move in different directions during zooming from the wide-angle end to the telephoto end. It is an expression that defines the ratio of the movement amount of the second lens group and the movement amount of the third lens group. However, the “movement amount” of the second lens group means the difference between the position on the optical axis of the second lens group at the wide-angle end and the position on the optical axis of the second lens group at the telephoto end, An unsigned value. The same applies to the "movement amount" of the third lens group. By satisfying the conditional expression (4), it is possible to suppress the variation of the position of the center of gravity of the zoom lens during zooming. Therefore, for example, in an image pickup device or the like that is used by being fixedly mounted on various moving bodies such as an in-vehicle image pickup device or a surveillance camera or a building, etc., the zoom is performed even when a zoom operation is performed by remote control or automatic control. The lens can be kept horizontal.

  On the other hand, when the numerical value of the conditional expression (4) becomes less than the lower limit value or more than the upper limit value, the position of the center of gravity of the zoom lens fluctuates during zooming, and the zoom lens is used by being fixedly mounted on various moving bodies or buildings. In an imaging device, etc., when the zoom operation is performed by remote control or automatic control, etc., the zoom lens tilts toward the side with the center of gravity, etc. This is not preferable because there is a risk of problems such as movement to the outside of the surface.

  It is preferable that the second lens group moves to the image side and the third lens group moves to the object side during zooming from the wide-angle end to the telephoto end, and at that time, the conditional expression (4) is satisfied. Preferably.

  In order to obtain these effects, the lower limit value of conditional expression (4) is more preferably 0.8, further preferably 0.85. The upper limit value of conditional expression (4) is more preferably 1.3, and further preferably 1.2.

2. Imaging Device Next, an imaging device according to the present invention will be described. An image pickup apparatus according to the present invention includes the zoom lens according to the present invention, and an image pickup element that is provided on the image plane side of the zoom lens and that converts an optical image formed by the zoom lens into an electrical signal. It is characterized by

  Here, the image pickup device and the like are not particularly limited, and a solid-state image pickup device such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The image pickup apparatus according to the present invention is suitable for an image pickup apparatus using these solid-state image pickup devices such as a digital camera and a video camera. Further, the image pickup device may be a lens fixed type image pickup device in which a lens is fixed to a housing, or may be a lens interchangeable type image pickup device such as a single lens reflex camera or a mirrorless single lens camera. Of course. In particular, the zoom lens according to the present invention can adopt a lens barrel structure that is excellent in dustproof and dripproof, and is designed to be compact and lightweight while preventing the center of gravity from being located on the object side, so that a single-lens reflex camera, etc. The present invention is suitable not only for an image pickup device that can be carried by a user, but also for an image pickup device that is installed and fixed to various moving bodies such as an in-vehicle image pickup device and a surveillance camera, a building, and the like.

  The imaging device of the present invention is an image processing unit that electrically processes captured image data acquired by an image sensor to change the shape of the captured image, and an image used to process the captured image data in the image processing unit. It is more preferable to have an image correction data holding unit that holds correction data, an image correction program, and the like. When the size of the zoom lens is reduced, distortion (distortion) of the shape of the captured image formed on the image plane is likely to occur. At this time, the image correction data holding unit holds the distortion correction data for correcting the distortion of the captured image shape in advance, and the image processing unit uses the distortion correction data held in the image correction data holding unit. It is preferable to correct the distortion of the captured image shape. According to such an imaging device, it is possible to further reduce the size of the zoom lens, obtain an excellent captured image, and reduce the size of the entire imaging device.

  Further, in the image pickup apparatus according to the present invention, the magnification chromatic aberration correction data is held in advance in the image correction data holding unit, and the magnification chromatic aberration correction data held in the image correction data holding unit is used in the image processing unit. It is preferable to correct lateral chromatic aberration of the captured image. By correcting the chromatic aberration of magnification, that is, the chromatic distortion aberration by the image processing unit, it becomes possible to reduce the number of lenses constituting the optical system. Therefore, according to such an image pickup apparatus, it is possible to further reduce the size of the zoom lens, obtain an excellent captured image, and reduce the size of the entire image pickup apparatus.

  Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

(1) Optical Configuration of Zoom Lens FIG. 1 shows a lens cross-sectional view of a zoom lens of Example 1 according to the present invention. In addition, "I" shown in the drawing is an image plane, and specifically represents an image plane of a solid-state image sensor such as a CCD sensor or a CMOS sensor, or a film plane of a silver salt film. Further, a parallel plate having no substantial refractive power, such as a cover glass “CG”, is provided on the object side of the image plane I. Since these points are the same in each lens cross-sectional view shown in other examples, description thereof will be omitted below.

  The zoom lens of Embodiment 1 has, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. And a fourth lens group G4 having a negative refractive power and a fifth lens group G5 having a positive refractive power. The subsequent lens group referred to in the present invention is composed of a fourth lens group G4 and a fifth lens group G5.

  The configuration of each lens group will be described below. The first lens group G1 is composed of one biconvex lens. The second lens group G2 is composed of, in order from the object side, a negative meniscus lens convex to the object side, a biconcave lens, and a positive meniscus lens convex to the object side. The third lens group G3 includes a biconvex lens, an aperture stop S, a cemented lens in which a biconcave lens and a biconvex lens are cemented, and a cemented lens in which a biconvex lens and a negative meniscus lens having a convex surface on the image side are cemented. ing. The fourth lens group G4 is composed of a biconcave lens. The fifth lens group G5 is composed of a positive meniscus lens convex on the object side.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves to the image side, the third lens group G3 moves to the object side, and The fourth lens group G4 moves to the image side, and the fifth lens group G5 is fixed with respect to the image plane.

  Further, when focusing on an object close to infinity, the fourth lens group G4 moves to the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 1 shows surface data of the zoom lens of Example 1 according to the present invention (the 22nd and 23rd surfaces in Table 1 are surface data of the cover glass CG). In Table 1, “surface number” is the order of the lens surfaces counted from the object side, “r” is the radius of curvature, “d” is the lens thickness or lens interval on the optical axis, and “nd” is the d line (wavelength λ = 587.56 nm), "νd" indicates the Abbe number at the d-line. Further, "*" displayed on the right side of the surface number indicates that the lens surface is an aspherical surface. Further, "D (XX) (a surface number is entered in XX)" shown in the column of "d""is a variable interval in which the interval on the optical axis of the lens surface changes during zooming or focusing. Means that. The units of length in the table are all “mm”, and “∞” in the column of radius of curvature means a plane.

  Table 2 shows the aspherical surface coefficient of each aspherical surface. The aspherical surface coefficient is a value when each aspherical surface shape is defined by the following equation.

^{z = ch 2 / [1+ {} 1- (1 + k) c 2 h 2} 1/2] + A4h 4 + A6h 6 + A8h 8 + A10h 10 ···

However, in the above equation, “c” is the curvature (1 / r), “h” is the height from the optical axis, “k” is the conic coefficient, “A4”, “A6”, “A8”, and “A10”. ... are aspherical coefficients of each order. Furthermore, "E-n" in Table 2 shows the "× 10 ^n".

  Table 3 shows various data of the zoom lens. In the table, the zoom ratio and maximum image height (y) of the zoom lens, wide-angle end, intermediate focal length position, focal length of the zoom lens at the telephoto end, F number, half field angle, optical total length (L) , Shows the back focus. Table 3 shows variable intervals on the optical axis of the zoom lens when focusing on infinity. In the table, all units of length are "mm" and all units of angle are "°".

  Table 4 shows the surface numbers included in each lens group and the focal lengths of each lens group. Table 17 shows the values of conditional expressions (1) to (5) and the values used to calculate the values.

  Since the matters relating to the above-mentioned tables are the same in the tables shown in other embodiments, the description thereof will be omitted below.

[Table 1]
Surface number rd nd νd
1 58.539 3.5232 1.5187 64.20
2 -2740.091 D (2)
3 84.654 0.900 1.6615 50.85
4 11.814 7.480
5 * -25.920 0.900 1.4986 81.56
6 * 62.984 0.940
7 38.600 2.409 1.8551 23.78
8 1451.071 D (8)
9 * 16.185 3.009 1.5552 71.68
10 * -42.443 1.868
11 ∞ 8.513 (aperture stop)
12 -25.9596 0.800 1.8629 24.80
13 19.171 2.890 1.5552 71.68
14 * -25.260 0.150
15 39.065 3.296 1.8118 33.27
16 -16.712 0.800 1.7044 30.05
17 -50.118 D (17)
18 * -43.637 0.800 1.7717 49.24
19 * 40.289 D (19)
20 31.009 3.751 1.9332 20.88
21 86.429 13.070
22 ∞ 3.560 1.5187 64.20
23 ∞ 1.000

[Table 2]
Surface number k A4 A6 A8 A10 A12
5 0 4.7315E-05 -7.7177E-07 4.0564E-09 -1.0246E-11 0.0000E + 00
6 0 3.5547E-05 -8.0950E-07 3.9794E-09 -1.0729E-12 -4.2432E-14
9 0 -1.6225E-05 1.1053E-07 -5.6590E-09 7.9654E-11 0.0000E + 00
10 0 2.0066E-05 5.0866E-08 -4.0245E-09 6.9796E-11 0.0000E + 00
14 0 2.6713E-05 3.4924E-07 -3.6677E-09 1.2666E-10 0.0000E + 00
18 0 2.0046E-05 3.8105E-08 -1.6475E-10 4.2803E-12 0.0000E + 00
19 0 3.7309E-05 -2.5483E-08 5.7917E-11 -1.8033E-12 0.0000E + 00
The aspherical surface coefficient not shown in Table 2 is 0.00.

[Table 3]
Magnification ratio 1.78, image height 14.20
Wide-angle mid-telephoto focal length 18.490 22.793 32.990
F number 3.387 3.539 3.859
Half angle of view 40.804 33.099 23.296
Total lens length 84.016 84.016 84.016
Back focus 17.630 17.630 17.630
D (2) 1.000 4.967 9.000
D (8) 16.627 10.683 1.500
D (17) 2.447 4.517 9.862
D (19) 4.263 4.170 3.976

[Table 4]
Group number Focal length
1 group 1-2 110.951
2nd group 3-8 -18.796
3 groups 9-17 21.158
4 groups 18-19 -27.163
Group 5 20-21 50.753

  2 to 4 are longitudinal aberration diagrams of the zoom lens of Embodiment 1 at the wide-angle end, the intermediate focal length position, and the telephoto end when focused on infinity. The longitudinal aberration charts shown in the respective figures are spherical aberration (mm), astigmatism (mm), distortion (%), and chromatic aberration of magnification (mm) in order from the left side of the drawing.

  In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line represents the spherical aberration at the d line (wavelength 587.5600 nm), the broken line represents the spherical aberration at the C line (wavelength 656.2800 nm), and the alternate long and short dash line. Indicates the spherical aberration at the F line (wavelength 486.1300 nm).

  In the astigmatism diagram, the vertical axis represents the image height (indicated by Y in the figure), the solid line represents the astigmatism on the sagittal image plane (S) with respect to the d line, and the broken line represents the meridional (tangential) image plane (M). Astigmatism is shown.

  In the distortion diagram, the vertical axis represents the image height (indicated by Y in the figure), and the solid line indicates the distortion aberration at the d line.

  The matters relating to these longitudinal aberration diagrams are the same in the longitudinal aberration diagrams shown in the other examples, and hence the description thereof is omitted below.

(1) Optical Configuration of Zoom Lens FIG. 5 shows a lens cross-sectional view of the zoom lens of Example 2 according to the present invention. The zoom lens of Example 2 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. And a fourth lens group G4 having a negative refractive power and a fifth lens group G5 having a positive refractive power. The subsequent lens group referred to in the present invention is composed of a fourth lens group G4 and a fifth lens group G5.

  The configuration of each lens group will be described below. The first lens group G1 is composed of one biconvex lens. The second lens group G2 is composed of, in order from the object side, a negative meniscus lens convex to the object side, a biconcave lens, and a biconvex lens. The third lens group G3 includes a biconvex lens, an aperture stop S, a cemented lens in which a biconcave lens and a biconvex lens are cemented, and a cemented lens in which a biconvex lens and a biconcave lens are cemented. The fourth lens group G4 is composed of a biconcave lens. The fifth lens group G5 is composed of a positive meniscus lens convex on the object side.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves to the image side, the third lens group G3 moves to the object side, and The fourth lens group G4 moves to the image side, and the fifth lens group G5 is fixed with respect to the image plane.

  Further, when focusing on an object close to infinity, the fourth lens group G4 moves to the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 5 shows surface data of the zoom lens of Example 2 according to the present invention, Table 6 shows aspherical coefficients of each aspherical surface, Table 7 shows various data of the zoom lens, and Table 8 shows each lens group. The surface numbers included in and the focal length of each lens group are shown. Table 17 shows the values of conditional expressions (1) to (5) and the values used to calculate the values. Further, FIGS. 6 to 8 show longitudinal aberration diagrams of the zoom lens of Example 2 at the wide-angle end, the intermediate focal length position, and the telephoto end when focused on infinity.

[Table 5]
Surface number rd nd νd
1 1152.433 2.4053 1.5187 64.20
2 -144.569 D (2)
3 107.101 0.900 1.5956 67.00
4 11.750 7.352
5 * -28.215 0.900 1.4986 81.56
6 * 82.701 0.420
7 48.032 2.786 1.8093 39.64
8 -96.535 D (8)
9 * 19.405 2.310 1.5552 71.68
10 * -56.353 1.868
11 ∞ 9.235 (aperture stop)
12 -586.308 0.800 1.8551 23.78
13 13.5729 2.706 1.4986 81.56
14 * -26.257 0.150
15 28.424 4.422 1.8126 25.46
16 -10.947 0.800 1.7044 30.05
17 38.978 D (17)
18 * -39.619 0.900 1.6252 58.16
19 * 68.946 D (19)
20 34.213 2.395 1.8108 40.73
21 120.718 12.947
22 ∞ 3.560 1.5187 64.20
23 ∞ 1.000

[Table 6]
Surface number k A4 A6 A8 A10 A12
5 0 4.1771E-05 -6.9684E-07 4.1609E-09 -1.9409E-11 0.0000E + 00
6 0 1.9876E-05 -7.0718E-07 3.1627E-09 -1.1081E-11 0.0000E + 00
9 0 -2.0818E-05 9.8703E-08 -2.0272E-09 -1.9686E-11 0.0000E + 00
10 0 3.9523E-06 1.2482E-07 -2.5474E-09 -1.3590E-11 0.0000E + 00
14 0 1.4248E-05 4.8519E-08 4.2122E-09 1.3870E-12 0.0000E + 00
18 0 -9.1343E-05 1.8219E-06 -1.3733E-08 4.8131E-11 0.0000E + 00
19 0 -6.7481E-05 1.7161E-06 -1.3813E-08 4.6267E-11 0.0000E + 00
The aspherical surface coefficient not shown in Table 6 is 0.00.

[Table 7]
Magnification ratio 1.78, image height 14.163
Wide-angle mid-telephoto focal length 18.518 22.816 33.009
F number 3.447 3.672 3.966
Half angle of view 40.702 33.289 23.307
Total lens length 84.487 84.487 84.487
Back focus 17.507 17.507 17.507
D (2) 1.000 4.530 9.000
D (8) 18.698 12.004 1.500
D (17) 3.335 5.514 12.807
D (19) 3.597 4.583 3.323

[Table 8]
Group number Focal length
1 group 1-2 248.716
2nd group 3-8 -24.621
3rd group 9-17 22.920
4 groups 18-19 -40.282
5 groups 20-21 58.506

(1) Optical Configuration of Zoom Lens FIG. 9 shows a lens sectional view of a zoom lens of Example 3 according to the present invention. The zoom lens of Embodiment 3 has, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. And a fourth lens group G4 having a negative refractive power and a fifth lens group G5 having a positive refractive power. The subsequent lens group referred to in the present invention is composed of a fourth lens group G4 and a fifth lens group G5.

  The configuration of each lens group will be described below. The first lens group G1 is composed of one biconvex lens. The second lens group G2 is composed of, in order from the object side, a negative meniscus lens convex to the object side, a biconcave lens, and a biconvex lens. The third lens group G3 includes a biconvex lens, an aperture stop S, a cemented lens in which a biconcave lens and a biconvex lens are cemented, and a cemented lens in which a biconvex lens and a biconcave lens are cemented. The fourth lens group G4 is composed of a biconcave lens. The fifth lens group G5 is composed of a positive meniscus lens convex on the object side.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves to the image side, the third lens group G3 moves to the object side, and The fourth lens group G4 moves to the image side, and the fifth lens group G5 is fixed with respect to the image plane.

  Further, when focusing on an object close to infinity, the fourth lens group G4 moves to the image side.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 9 shows surface data of the zoom lens of Example 3 according to the present invention, Table 10 shows aspherical coefficient of each aspherical surface, Table 11 shows various data of the zoom lens, and Table 12 shows each lens group. The surface numbers included in and the focal length of each lens group are shown. Table 17 shows the values of conditional expressions (1) to (5) and the values used to calculate the values. Further, FIGS. 10 to 12 show longitudinal aberration diagrams at the time of focusing at infinity at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens according to the third embodiment.

[Table 9]
Surface number rd nd νd
1 492.973 2.6878 1.5187 64.20
2 -126.635 D (2)
3 2342.077 0.900 1.5187 64.20
4 11.165 7.247
5 * -36.829 0.900 1.4986 81.56
6 * 62.305 0.420
7 37.921 2.753 1.8393 37.34
8 -319.366 D (8)
9 * 21.502 2.246 1.5552 71.68
10 * -45.771 1.868
11 ∞ 8.930 (aperture stop)
12 -529.329 0.800 1.8629 24.80
13 13.5729 2.852 1.4986 81.56
14 * -21.364 0.150
15 33.206 4.536 1.8126 25.46
16 -10.175 0.800 1.7044 30.05
17 36.919 D (17)
18 * -45.100 0.900 1.5914 61.25
19 * 65.574 D (19)
20 35.617 2.733 1.7902 43.93
21 140.419 13.082
22 ∞ 3.560 1.5187 64.20
23 ∞ 1.000

[Table 10]
Surface number k A4 A6 A8 A10 A12
5 0 4.7184E-05 -6.2615E-07 2.9994E-09 -2.0905E-11 0.0000E + 00
6 0 2.1714E-05 -6.4958E-07 9.7146E-10 -8.7780E-12 0.0000E + 00
9 0 -2.2229E-05 8.2930E-08 -4.2273E-09 1.4025E-11 0.0000E + 00
10 0 5.7 005E-06 1.1070E-07 -4.8756E-09 2.6500E-11 0.0000E + 00
14 0 1.3259E-05 -4.7574E-08 5.7140E-09 -1.9301E-11 0.0000E + 00
18 0 -1.0682E-04 2.5030E-06 -2.3922E-08 1.0379E-10 0.0000E + 00
19 0 -8.7809E-05 2.2325E-06 -2.0367E-08 7.8038E-11 0.0000E + 00
The aspherical surface coefficient not shown in Table 10 is 0.00.

[Table 11]
Zoom ratio 1.78, image height 14.163
Wide-angle mid-telephoto focal length 18.518 22.813 33.005
F number 3.359 3.576 3.854
Half angle of view 40.705 33.117 23.233
Total lens length 83.487 83.487 84.487
Back focus 17.642 17.642 17.642
D (2) 1.000 4.412 9.000
D (8) 18.619 12.010 1.500
D (17) 3.288 5.350 12.552
D (19) 3.216 4.350 3.070

[Table 12]
Group number Focal length
1 group 1-2 195.246
2nd group 3-8 -24.815
3 groups 9-17 23.227
4 groups 18-19 -45.221
5 groups 20-21 60.033

(1) Optical Configuration of Zoom Lens FIG. 13 is a lens cross-sectional view of the zoom lens of Example 4 according to the present invention. The zoom lens of Embodiment 4 has, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. And a fourth lens group G4 having a negative refractive power and a fifth lens group G5 having a positive refractive power. The subsequent lens group referred to in the present invention is composed of a fourth lens group G4 and a fifth lens group G5.

  The configuration of each lens group will be described below. The first lens group G1 is composed of one positive lens (or one biconvex lens) having a convex surface on the object side. The second lens group G2 is composed of, in order from the object side, a biconcave lens, a biconcave lens, and a biconvex lens. The third lens group G3 includes a biconvex lens, an aperture stop S, a cemented lens in which a biconcave lens and a biconvex lens are cemented, and a cemented lens in which a biconvex lens and a negative meniscus lens having a convex surface on the image side are cemented. Has been done. The fourth lens group G4 is composed of a biconcave lens. The fifth lens group G5 is composed of a biconvex lens on the object side.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed with respect to the image plane, the second lens group G2 moves to the image side, the third lens group G3 moves to the object side, and The fourth lens group G4 moves to the image side, and the fifth lens group G5 is fixed with respect to the image plane.

  Further, when focusing on an object close to infinity, the fourth lens group G4 moves to the image side. Further, by moving the fifth lens group G5 to the object side, it is possible to focus on an infinite object from infinity.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 13 shows surface data of the zoom lens of Example 4 according to the present invention, Table 14 shows aspherical coefficients of each aspherical surface, Table 15 shows various data of the zoom lens, and Table 16 shows each lens group. The surface numbers included in and the focal length of each lens group are shown. Table 17 shows the values of conditional expressions (1) to (5) and the values used to calculate the values. Further, FIGS. 13 to 16 show longitudinal aberration diagrams of the zoom lens of Example 3 at the wide-angle end, the intermediate focal length position, and the telephoto end when focused on infinity.

[Table 13]
Surface number rd nd νd
1 46.872 4.5715 1.5168 64.20
2 1387.234 D (2)
3 -257.244 0.900 1.7433 49.22
4 12.913 6.512
5 * -28.318 0.900 1.6188 63.85
6 * 117.460 0.924
7 37.169 6.425 1.8548 24.80
8 -131.002 D (8)
9 * 15.789 3.990 1.5533 71.68
10 * -45.142 1.868
11 ∞ 8.513 (aperture stop)
12 -23.2645 0.800 1.8548 24.80
13 19.009 3.460 1.5533 71.68
14 * -18.906 0.150
15 34.207 3.060 1.8061 33.27
16 -28.465 0.800 1.6990 30.05
17 -865.402 D (17)
18 * -24.614 0.800 1.7680 49.24
19 * 70.983 D (19)
20 65.888 3.698 1.9229 20.88
21 -55.667 12.440
22 ∞ 3.560 1.5168 64.20
23 ∞ 1.000

[Table 14]
Surface number k A4 A6 A8 A10 A12
5 0 2.0431E-04 -3.0521E-06 2.6145E-08 -9.2291E-11 0.0000E + 00
6 0 1.8663E-04 -3.1698E-06 2.7052E-08 -9.9697E-11 0.0000E + 00
9 0 -1.6369E-05 1.4305E-07 -5.4488E-09 6.3472E-11 0.0000E + 00
10 0 2.1638E-05 1.3639E-08 -2.9023E-09 5.5666E-11 0.0000E + 00
14 0 1.6404E-05 7.2373E-07 -1.4362E-08 2.2837E-10 0.0000E + 00
18 0 -1.6526E-05 9.9854E-07 -9.8565E-09 5.4782E-11 0.0000E + 00
19 0 -9.5090E-06 7.8788E-07 -8.2305E-09 3.8223E-11 0.0000E + 00
The aspherical surface coefficient not shown in Table 14 is 0.00.

[Table 15]
Magnification ratio 1.78, image height 14.163
Wide-angle mid-telephoto focal length 18.504 22.809 33.007
F number 3.500 3.661 4.084
Half angle of view 42.211 33.751 23.426
Total lens length 91.031 91.031 91.031
Back focus 17.000 17.000 17.000
D (2) 1.770 5.341 9.770
D (8) 17.070 11.078 1.500
D (17) 3.556 5.457 10.462
D (19) 4.265 4.784 4.929

[Table 16]
Group number Focal length
1 group 1-2 93.759
2nd group 3-8 -19.291
3 groups 9-17 22.631
4 groups 18-19 -23.711
5 groups 20-21 33.180

[Table 17]
Example 1 Example 2 Example 3 Example 4
(1) L / Y × Nd2ave 9.335 9.218 8.883 10.805
(2) L / Y × Nd2max 9.812 9.506 8.941 11.205
(3) | f2 / fw | 1.016 1.330 1.340 1.043
(4) M2 / M3 1.123 0.870 0.877 1.057
(5) Nd2ave 1.5778 1.5453 1.5070 1.6811
L 84.016 84.487 83.487 91.031
Y 14.2 14.163 14.163 14.163
Nd2max 1.6584 1.5935 1.5168 1.7433
f2 -18.796 -24.621 -24.815 -19.291
fw 18.500 18.518 18.518 18.504
M2 8.000 8.000 8.000 8.000
M3 7.127 9.200 9.124 7.570

  According to the present invention, it is possible to provide a zoom lens and an image pickup device which can adopt a lens barrel structure excellent in dustproof and dripproof, and which is downsized and lightweight.

G1 ... First lens group G2 ... Second lens group G3 ... Third lens group G4 ... Fourth lens group G5 ... Fifth lens group S ... Aperture stop

Claims (8)

The first lens group having a positive refracting power, the second lens group having a negative refracting power, the third lens group having a positive refracting power, and the subsequent lens group, which are sequentially arranged from the object side, Is composed of
At the time of zooming from the wide-angle end to the telephoto end, the first lens group is fixed with respect to the image plane, and at least the second lens group and the above-mentioned lens group are arranged so that the interval between the lens groups adjacent to each other changes. The third lens group moves in the optical axis direction,
A zoom lens that satisfies the following conditional expression.
(1) 7.8 <L / y × Nd2ave <11
(2) 8.0 <L / y × Nd2max <13
However,
L: Optical total length of the zoom lens y: Maximum image height of the zoom lens Nd2ave: Average refractive index of the negative lens included in the second lens group with respect to d line Nd2max: Negative lens included in the second lens group Refractive index for d-line of negative lens made of glass material with the highest refractive index for d-line The subsequent lens group includes, in order from the object side, a fourth lens group having a negative refractive power and a fifth lens group having a positive refractive power,
The zoom lens according to claim 1, wherein the fourth lens group moves in the optical axis direction during zooming from the wide-angle end to the telephoto end.   The zoom lens according to claim 1, wherein any one of the lens groups included in the subsequent lens group is moved in the optical axis direction to focus.   The zoom lens according to any one of claims 1 to 3, wherein the first lens group includes one positive lens. The zoom lens according to any one of claims 1 to 4, which satisfies the following conditional expression.
(3) 0.8 <| f2 / fw | <1.4
However,
f2: focal length of the second lens group fw: focal length of the zoom lens at the wide-angle end The zoom lens according to any one of claims 1 to 5, which satisfies the following conditional expression.
(4) 0.75 <M2 / M3 <1.5
However,
M2: amount of movement of the second lens group at the time of zooming from the wide-angle end to the telephoto end M3: amount of movement of the third lens group at the time of zooming from the wide-angle end to the telephoto end The zoom lens according to any one of claims 1 to 6, which satisfies the following conditional expression.
(5) 1.50 <Nd2ave <1.70   A zoom lens according to any one of claims 1 to 7, and an image sensor for converting an optical image formed by the zoom lens into an electrical signal on the image side of the zoom lens. Characteristic imaging device.

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