JP7278062B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens and an imaging device, and more particularly to a zoom lens and an imaging device suitable for a compact imaging device using a solid-state imaging device or the like.

2. Description of the Related Art Conventionally, imaging apparatuses using solid-state imaging devices such as digital still cameras and digital video cameras have been widely used. 2. Description of the Related Art As an optical system of an imaging device, for example, a zoom lens that includes a plurality of lens groups and changes the focal length by changing the distance between the lens groups during zooming is widely known. Since the zoom lens can adjust the focal length according to the distance to the subject, it is highly convenient when taking an image. In particular, there is a great demand for a so-called standard zoom lens that includes a focal length of 50 mm in terms of 35 mm format.

As a standard zoom lens, for example, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and an image from the third lens group A zoom lens has been proposed that has a lens group with a positive refractive power on the side of the zoom lens (see Patent Document 1).

JP 2015-118214 A

By the way, there is a strong market demand for miniaturization, high performance, and low cost for standard zoom lenses. Although the zoom lens disclosed in Patent Document 1 achieves miniaturization and high performance, the first lens group includes a lens made of anomalous dispersion glass material, and the second lens group includes an aspherical lens. Further cost reduction is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens and an image pickup apparatus that are compact and have high optical performance while achieving cost reduction.

In order to solve the above problems, a zoom lens according to the present invention comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and three or more lens groups. and a rear group having positive refractive power as a whole, and performing zooming by changing the distance between adjacent lens groups, wherein the first lens group is positioned closest to the object side. The lens L1n having negative refractive power and the lens L1n having positive refractive power are arranged, and the Abbe number at the d-line of the lens having positive refractive power included in the first lens group is 48. As described above, the second lens group does not include an aspherical surface, the rear group has at least one lens having negative refractive power, and the following conditional expression is satisfied.
1.85 < NdL1n < 2.20 (2)
1.86<NdLnr<2.20 (8)
-0.90 < β2t < -0.45 (7)
however,
NdL1n: Refractive index at the d-line of the lens L1n having negative refractive power NdLnr: Refractive index at the d-line of the lens Lnr having the highest refractive index among the lenses having negative refractive power included in the rear group β2t : lateral magnification of the second lens group at the telephoto end

Further, in order to solve the above-mentioned problems, an imaging apparatus according to the present invention is characterized by comprising an imaging element for converting an optical image formed by the zoom lens into an electrical signal on the image side of the zoom lens. do.

According to the present invention, it is possible to provide a compact zoom lens and an imaging device with high optical performance while achieving cost reduction.

FIG. 2 shows a cross-sectional view of the zoom lens of Example 1 of the present invention at the wide-angle end when focusing on infinity. 4A and 4B are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when focusing on infinity at the wide-angle end of the zoom lens of Example 1. FIG. 4A and 4B are spherical aberration diagrams, astigmatism diagrams, and distortion diagrams when focusing on infinity in an intermediate focal length state of the zoom lens of Example 1. FIG. 4A and 4B are spherical aberration diagrams, astigmatism diagrams, and distortion aberration diagrams when focusing on infinity at the telephoto end of the zoom lens of Example 1. FIG. FIG. 10 is a cross-sectional view of the zoom lens of Example 2 of the present invention at the wide-angle end when focusing on infinity. 10A and 10B are spherical aberration diagrams, astigmatism diagrams, and distortion aberration diagrams when focusing on infinity at the wide-angle end of the zoom lens of Example 2. FIG. 10A and 10B are spherical aberration diagrams, astigmatism diagrams, and distortion aberration diagrams when focusing on infinity in an intermediate focal length state of the zoom lens of Example 2. FIG. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity at the telephoto end of the zoom lens of Example 2; FIG. 10 is a cross-sectional view of the zoom lens of Example 3 of the present invention at the wide-angle end when focusing on infinity. 10A and 10B are spherical aberration diagrams, astigmatism diagrams, and distortion aberration diagrams when focusing on infinity at the wide-angle end of the zoom lens of Example 3. FIG. FIG. 10 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity in an intermediate focal length state of the zoom lens of Example 3; FIG. 11 is a spherical aberration diagram, an astigmatism diagram, and a distortion aberration diagram when focusing on infinity at the telephoto end of the zoom lens of Example 3; It is a figure for demonstrating (DELTA)A.

Embodiments of a zoom lens and an imaging device according to the present invention will be described below. However, the zoom lens and imaging device described below are aspects of the zoom lens and imaging device according to the present invention, and the zoom lens and imaging device according to the present invention are not limited to the following aspects.

1. Zoom lens 1-1. Optical Configuration of Zoom Lens The zoom lens of the present embodiment comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a plurality of lens groups. and a rear group having positive refracting power. Magnification is changed by changing the distance on the optical axis between adjacent lens groups.

By adopting the above power arrangement, it becomes easy to strengthen the negative refractive power of the second lens group arranged between the first lens group having positive refractive power and the rear group, and the second lens group can be moved with a small amount of movement. It is possible to increase the zooming action of the two lens groups. That is, by adopting the power arrangement suitable for a so-called standard zoom lens, the zoom lens realizes a high zoom ratio and can cover a wide zoom range from wide-angle to telephoto. At the same time, the entire structure can be made compact, and high optical performance can be achieved. Therefore, the zoom lens has a focal length of 50 mm in terms of the 35 mm format, while making it easier to increase the half angle of view (ω) of the zoom lens at the wide-angle end to more than 24°.
The optical configuration and the like of each lens group will be described below.

(1) First Lens Group The first lens group is a lens group having a positive refractive power that is arranged closest to the object side among the plurality of lens groups that constitute the zoom lens. However, an optical element having no or very low refractive power may be arranged on the object side of the first lens group. Examples of such optical elements include protective filters for protecting lenses from dirt and scratches, ND filters for reducing the amount of incident light, and various filters such as PL filters for color adjustment. is mentioned.

The specific lens configuration of the first lens group is not particularly limited as long as it has positive refractive power. Since the first lens group as a whole has positive refractive power, the first lens group may have at least one lens with positive refractive power. It is preferable to configure the first lens group by using a plurality of lenses having positive refractive power, because it facilitates correction of chromatic aberration and spherical aberration at the telephoto end.

Further, it is preferable that the first lens group has a lens L1n having a negative refractive power in terms of correction of chromatic aberration and image surface properties. The first lens group may have at least one lens L1n having negative refractive power, and may have a plurality of lenses L1n.

Furthermore, when the first lens group includes at least one lens L1n having negative refractive power, at least one lens L1n is cemented with at least one lens having positive refractive power. is preferred. When compared with a configuration in which a lens L1n having a negative refractive power and a lens having a positive refractive power are arranged with an air gap between them, various manufacturing errors such as eccentric errors and errors in the air gap between single lenses are reduced. can be made smaller. Therefore, deterioration in optical performance due to manufacturing errors can be reduced, and variations in performance between products can be reduced. Therefore, a zoom lens with high optical performance can be manufactured with high yield.

Furthermore, among the lenses L1n having negative refractive power included in the first lens group, at least one of the lenses L1n has an Abbe number at the d-line smaller than 45, and the positive refractive power included in the first lens group is At least one of the lenses preferably has an Abbe number greater than 45 in terms of correction of chromatic aberration. Furthermore, it is more preferable that at least one of the lenses having positive refractive power included in the first lens group has an Abbe number greater than 57.

Among the lenses having positive refractive power included in the first lens group, the Abbe number at the d-line of at least one lens satisfies the above conditions, and the other lenses having positive refractive power The Abbe number at the d-line is not particularly limited. However, if all the Abbe numbers at the d-line of the lenses having positive refractive power included in the first lens group are larger than 45, chromatic aberration can be corrected more favorably, which is more preferable. Further, in order to perform chromatic aberration correction even better, it is more preferable that all the Abbe numbers at the d-line of the lenses having positive refractive power included in the first lens group are greater than 48. It is even more preferable that the Abbe numbers at the d-line of the lenses having the refractive power of are all greater than 51.

The number of lenses constituting the first lens group is not particularly limited. and one lens L1n having negative refractive power.

(2) Second Lens Group The second lens group is a lens group having a negative refractive power and arranged on the image side of the first lens group. The specific lens configuration of the second lens group is not particularly limited as long as it has negative refractive power as a whole. Since the second lens group as a whole has negative refractive power, the second lens group may have at least one lens with negative refractive power. In terms of correcting chromatic aberration, it is preferable that the second lens group has at least one lens having a positive refractive power. At this time, it is preferable to dispose a lens having negative refractive power on the image side of the lens having positive refractive power because chromatic aberration can be corrected more satisfactorily at the telephoto end.

Furthermore, if the second lens group is constructed using a plurality of lenses having negative refractive power, it is preferable because correction of curvature of field at the wide-angle end is facilitated. Here, in order to reduce the size of the zoom lens in the radial direction, it is preferable to arrange the entrance pupil position as close to the object side as possible at the wide-angle end. From the viewpoint of arranging the entrance pupil position at the wide-angle end closer to the object side and miniaturizing the zoom lens, when the second lens group includes a plurality of lenses having negative refractive power, they are arranged adjacent to each other. Preferably, a lens with positive refractive power is arranged on the image side of two or more lenses with negative refractive power. Further, in order to reduce the size of the zoom lens, it is preferable that the lens located closest to the object side in the second lens group has a refractive index of greater than 1.84 for the d-line.

Among the lens groups constituting the zoom lens, the second lens group is composed of lenses having a relatively large diameter. Therefore, if the second lens group is constructed using an aspherical lens, the cost will be very high. Therefore, it is preferable that the second lens group does not include an aspherical lens in order to reduce the cost of the zoom lens. Here, an aspherical surface means a shape of a lens surface defined by an aspherical coefficient. The second lens group need only include no lens having an aspherical surface, and may include a lens having a flat surface, a diffraction grating surface, or the like.

(3) Rear Group The rear group is a general term for a group consisting of a plurality of lens groups arranged closer to the image side than the second lens group. The rear group as a whole only needs to have positive refractive power, and its specific lens group configuration is not particularly limited. Since the rear group has positive refractive power as a whole, it has at least one lens group with positive refractive power, and may have two or more lens groups with positive refractive power. It may have one or more lens groups with refractive power. In order to reduce the size of the zoom lens, it is preferable to dispose a lens group having a positive refractive power closest to the object side of the rear group in terms of increasing the magnification and increasing the aperture. It is not limited.

Although the number of lens groups constituting the rear group is not particularly limited, a large number of lens groups constituting the rear group is preferable because aberration correction can be performed satisfactorily over the entire zoom range. From this point of view, the number of lens groups constituting the rear group is preferably two or more, more preferably three or more. When the number of lens groups constituting the rear group is three or more, field curvature can be satisfactorily corrected at intermediate focal lengths, so a zoom lens with higher optical performance over the entire zoom range can be obtained. preferred. For example, it is more preferable that the rear group is composed of two or more lens groups having positive refractive power and one or more lens groups having negative refractive power.

i) Aspheric Surface The rear group preferably includes at least one aspheric surface. By including an aspherical surface, it is possible to satisfactorily correct aberrations with a small number of lenses. In particular, the aspherical surface is preferably an aspherical surface ra that is convex toward the object side. By arranging the aspherical surface ra convex toward the object side in the rear group, it is possible to satisfactorily correct not only axial aberrations but also off-axis aberrations. Therefore, the number of lenses and the number of aspherical surfaces required for aberration correction can be reduced. As a result, it is possible to realize a compact zoom lens with high optical performance at low cost.

Further, the aspherical surface ra preferably has a shape in which the refractive power in the peripheral portion is weaker than the refractive power in the paraxial spherical surface defined by the paraxial radius of curvature. In this case, it is more preferable that the entire surface of the aspherical surface ra has a shape in which the refractive power is weaker than that of the paraxial spherical surface defined by the paraxial radius of curvature.

Here, the shape in which the refractive power of the aspherical surface ra is weaker than the refractive power of the paraxial spherical surface defined by the paraxial radius of curvature means that the sag amount of the aspherical surface ra at a height h from the optical axis is , that the aspherical surface ra is smaller than the sag amount of the paraxial spherical surface r defined by the paraxial radius of curvature. A more detailed description will be given with reference to FIG. FIG. 13 shows part of a lens with an aspheric surface ra. However, FIG. 13 shows one aspect of the lens having the aspherical surface ra, and the shape of the lens having the aspherical surface ra is not limited to the aspect shown in FIG.

In FIG. 13, the dashed line indicates the optical axis, the solid line indicates the surface shape of the lens having the aspheric surface ra, and the dashed line indicates the paraxial spherical surface r defined by the paraxial radius of curvature for the aspheric surface ra. The sag amount at a height position h from the optical axis is generally defined as a vertical plane perpendicular to the optical axis from the vertex of the lens surface and a straight line parallel to the lens surface and the optical axis at a height position h from the optical axis. The distance in the direction of the optical axis from the intersection of When the aspheric surface ra is convex toward the object side, the sag amount of the aspheric surface ra at the height h from the optical axis is greater than the sag amount of the paraxial spherical surface r defined by the paraxial radius of curvature of the aspheric surface ra. With a smaller shape, the aspheric surface ra has a weaker refractive power at its periphery than the refractive power at the paraxial spherical surface defined by the paraxial radius of curvature. In the figure, RP indicates the maximum effective radius RP of the aspherical surface, and ΔA is the sag amount of the aspherical surface ra at a height position equal to the maximum effective radius RP from the optical axis, and the paraxial curvature of the aspherical surface ra. It shows the difference from the sag amount of the paraxial spherical surface r defined by the radius.

By using an aspherical surface with such a shape, it is possible to suppress the occurrence of spherical aberration and coma while placing a strong refractive power on the aspherical surface, so a zoom lens with high optical performance with a small number of lenses. can be realized.

ii) lens surface rn
It is preferable that the rear group has at least one surface rn having a concave shape on at least the image side. By having the lens Lnr having negative refractive power, it is possible to cancel the negative distortion and image surface characteristics that occur in the second lens group, thereby achieving improvements in distortion and image surface characteristics. As a result, high performance of the zoom lens is achieved.

iii) Lens Lnr
The rear group preferably has at least one lens Lnr with negative refractive power. By arranging the lens Lnr having negative refractive power in the rear group, field curvature and chromatic aberration can be reduced, making it easier to realize a zoom lens with high optical performance. The lens Lnr may be included in any one of the lens groups constituting the rear group. Also, the lens group including the lens Lnr may have positive refractive power or negative refractive power, but preferably has positive refractive power.

(4) Focus group In the zoom lens, presence or absence of the focus group is not particularly limited. When a focus group is provided, at least one lens among the lenses constituting the zoom lens can be used as the focus group, and the focus group can be moved in the optical axis direction during focusing to focus on the subject. The position and refractive power of the lens used as the focus group in the zoom lens are not particularly limited.

When a focus group is provided in the zoom lens, the number of lenses constituting the focus group is not particularly limited, and the number of lenses constituting the focus group may be one or plural. However, in order to suppress aberration fluctuations that occur when focusing on a close subject, it is preferable that the focus group is composed of a plurality of lenses.

Also, in order to reduce the size and weight of the focus group, it is preferable to construct the focus group from one single lens unit. Here, the single lens unit refers to a lens unit such as one single lens or a cemented lens in which a plurality of single lenses are integrated without an air gap. That is, even if the single lens unit has a plurality of optical surfaces, only the side closest to the object and the side closest to the image are in contact with the air, and the other surfaces are not in contact with the air. In this specification, a single lens may be either a spherical lens or an aspherical lens. The aspherical lens also includes a so-called compound aspherical lens having an aspherical film attached to the surface. In particular, from the viewpoint of reducing the size and weight of the focus group while suppressing aberration fluctuations that occur when focusing on the above-mentioned close subject, the focus group is made up of multiple single lenses integrated without an air gap. It is more preferable to be composed of cemented lenses.

When the focus group consists of one single lens unit as described above, the focus group does not contain an air gap. Therefore, compared with a structure in which a plurality of single lenses are arranged with an air gap in the focus group, the size and weight of the focus group can be reduced. As a result, it is possible to reduce the size and weight of the mechanical member (hereinafter referred to as the "focus drive mechanism") for moving the focus group in the optical axis direction during focusing, thereby reducing the overall size of the zoom lens unit. It is possible to achieve reduction in size and weight. In addition to the zoom lens, the zoom lens unit includes a drive mechanism (hereinafter referred to as a zoom drive mechanism) for relatively moving each lens group during zooming, a focus drive mechanism, and a mirror housing them. A cylinder etc. shall be included.

In addition, when compared with a configuration in which a plurality of single lenses are arranged with an air gap in the focus group, by configuring the focus group with the single single lens unit described above, decentration errors and air gaps between the single lenses can be reduced. Various manufacturing errors such as errors can be reduced. Therefore, deterioration in optical performance due to manufacturing errors can be reduced, and variations in performance between products can be reduced. Therefore, a zoom lens with high optical performance can be manufactured with high yield.

When a focus group is provided in the zoom lens, the arrangement of the focus group is not particularly limited. It is preferable to use a part as a focus group. Since the first lens group is composed of a lens with a relatively large diameter, it is easy to reduce the size and weight of the focus group by arranging the focus group in the lens groups after the second lens group.

In particular, it is preferable that one or a part of the lens groups constituting the rear group be used as the focus group. By adopting the power arrangement described above, the zoom lens can make the diameter of the light beam incident on the rear group smaller than the diameter of the light beam incident on the first lens group and the second lens group. Therefore, when one or a part of the lens groups constituting the rear group is used as the focus group, the focus group or the anti-vibration group is arranged in the first lens group or the second lens group. , the focus group can be made smaller and lighter.

In this case, the focus group more preferably has negative refractive power. By arranging the focus group having negative refractive power in the rear group, field curvature and distortion occurring in the second lens group having negative refractive power can be canceled by the focus group. Therefore, a zoom lens with higher optical performance can be obtained.

Furthermore, when the rear group includes the aspherical surface ra convex toward the object side, arranging a focusing group having a negative refractive power closer to the image side than the aspherical surface ra reduces the occurrence of aberrations when focusing on a close subject. It is preferable in that Since the aspherical surface ra is convex toward the object side, it has a positive refractive power and can suppress the occurrence of spherical aberration and coma on the aspherical surface. Since the amount of these aberrations generated on the aspherical surface is small, the amount of aberration generated by the lens having negative refractive power used to cancel them can also be reduced. Therefore, it is preferable to provide a zoom lens with high optical performance by arranging a focus group having a negative refractive power on the image side of the aspherical surface ra and focusing on a close subject by the focus group.

When the zoom lens is provided with a focus group, the lens surfaces included in the focus group may be spherical only or may include aspherical surfaces. In order to reduce the cost of the zoom lens, it is preferable that the focus group does not include an aspherical surface.

On the other hand, by making at least one aspherical surface among the lens surfaces included in the focus group, it is possible to easily satisfy the optical performance required for the zoom lens even when the focus group is configured with a small number of lenses. Become. Since the size and weight of the focus group can be reduced, the overall size of the zoom lens unit, including the focus drive mechanism, can be reduced. At this time, by making the aspherical surface included in the focus group into a shape that weakens the refractive power obtained from the paraxial spherical surface defined by the paraxial radius of curvature, spherical aberration, coma aberration and field curvature during focusing are improved. , it is possible to realize a zoom lens with higher optical performance.

Note that the number of focus groups included in the zoom lens is not limited to one, and a plurality of lens groups or a portion of a plurality of lens groups may be used as the focus group. That is, focusing may be performed by a floating method. By adopting the floating system, it is possible to improve the spherical aberration and the image surface property at the time of focusing at a close junction, so that it is possible to realize a zoom lens with higher optical performance, which is preferable.

(5) Anti-Vibration Group In the zoom lens, presence or absence of an anti-vibration group is not particularly limited. In order to correct image blur caused by, for example, vibration being transmitted to the image pickup apparatus during photographing, the image can be corrected electrically or the image pickup element can be moved. If the zoom lens is not provided with a vibration reduction group, image blur can be corrected by these methods.

When the zoom lens is provided with an anti-vibration group, the image may be shifted by decentering at least one lens among the lenses constituting the zoom lens, and the method is not particularly limited.

For example, if at least one lens among the lenses constituting the zoom lens is used as an anti-vibration group and the image is shifted by moving the anti-vibration group in a direction substantially perpendicular to the optical axis, the zoom lens including the lens barrel Since it is possible to reduce the size of the entire lens unit, it is preferable in terms of size reduction.

When the zoom lens is provided with an anti-vibration group, the arrangement of the anti-vibration group is not particularly limited, but it is more preferable to provide the anti-vibration group within the rear group. By adopting the power arrangement described above, the zoom lens can make the diameter of the light beam incident on the rear group smaller than the diameter of the light beam incident on the first lens group and the second lens group. Therefore, by arranging the anti-vibration group in the rear group, it is possible to reduce the size and weight of the anti-vibration group as compared with the case where the anti-vibration group is arranged in the first lens group or the second lens group.

Further, in the zoom lens, it is preferable that the anti-vibration group is arranged closer to the image side than the aperture stop. On the image side of the aperture stop, the variation in the height of the ray during zooming is small, so the variation in aberration during zooming is also small. Therefore, if the anti-vibration group is arranged on the image side of the aperture stop, even when the image is shifted by the anti-vibration group, fluctuations in aberration during zooming are small, and high optical performance can be achieved over the entire zoom range.

When the zoom lens is provided with an anti-vibration group, the refractive power of the anti-vibration group is not particularly limited, and may be positive or negative. When the anti-vibration group is provided in the rear group, the rear group as a whole has positive refractive power. can be reduced in quantity. Therefore, it is possible to suppress an increase in the diameter of the lens barrel, which is preferable.

Furthermore, when the rear group includes the aspherical surface ra convex to the object side, it is possible to reduce the occurrence of aberrations during image blur correction by arranging an anti-vibration group having a negative refractive power closer to the object side than the aspherical surface ra. It is preferable in that Since the aspherical surface ra is convex toward the object side, it has a positive refractive power and can suppress the occurrence of spherical aberration and coma on the aspherical surface. Since the amount of these aberrations generated on the aspherical surface is small, the amount of aberration generated by the lens having negative refractive power used to cancel them can also be reduced. Therefore, it is preferable to provide a zoom lens with high optical performance by arranging an anti-vibration group having a negative refractive power on the object side of the aspherical surface ra and performing image blur correction by the anti-vibration group.

When the zoom lens is provided with the anti-vibration group, the number of lenses constituting the anti-vibration group is not particularly limited. If the anti-vibration group is made up of a plurality of lenses, it is possible to suppress aberration fluctuations during anti-vibration, which is preferable. At this time, the anti-vibration group preferably has at least one lens with negative refractive power and at least one lens with positive refractive power. When the anti-vibration group has at least one lens with negative refractive power and one lens with positive refractive power, it is possible to suppress the occurrence of chromatic aberration during anti-vibration, and the zoom lens has higher optical performance. can be realized.

The anti-vibration group is preferably composed of one lens having negative refractive power and one lens having positive refractive power. By forming the anti-vibration group from only two lenses in this way, it is possible to reduce the size and weight of the anti-vibration group, and to reduce the overall size of the zoom lens unit including the anti-vibration driving mechanism.

When the anti-vibration group is composed of one lens having negative refractive power and one lens having positive refractive power, these two lenses are preferably cemented together. That is, it is preferable that the anti-vibration group is composed of the above-described single lens unit in which a lens having negative refractive power and a lens having positive refractive power are cemented together. By constructing the anti-vibration group from a single lens unit, it is possible to further reduce the size and weight of the anti-vibration group, and to further reduce the size of the zoom lens unit as a whole. Moreover, by constructing the anti-vibration group from single lens units, it is possible to reduce various manufacturing errors such as eccentric errors and air gap errors between single lenses. Therefore, deterioration in optical performance due to manufacturing errors can be reduced, and variations in performance between products can be reduced. Therefore, a zoom lens with high optical performance can be manufactured with high yield.

When the zoom lens is provided with an anti-vibration group, the lens surfaces included in the anti-vibration group may be spherical only or may include aspherical surfaces. In order to reduce the cost of the zoom lens, it is preferable that the anti-vibration group does not include an aspherical surface.

On the other hand, by making at least one aspherical surface among the lens surfaces included in the anti-vibration group, it is possible to satisfy the optical performance required for the zoom lens even when the anti-vibration group is configured with a small number of lenses. become easier. Since the anti-vibration group can be made smaller and lighter, it is possible to reduce the size of the entire anti-vibration unit including the anti-vibration drive mechanism. At this time, by making the aspherical surface included in the anti-vibration group a shape that weakens the refractive power obtained from the paraxial spherical surface defined by the paraxial radius of curvature, spherical aberration, coma, and Since the curvature of field can be satisfactorily corrected, a zoom lens with higher optical performance can be realized.

(6) Aperture Stop In the zoom lens, the arrangement of the aperture stop is not particularly limited. However, the aperture stop here means the aperture stop that defines the diameter of the light beam of the zoom lens, that is, the aperture stop that defines the Fno of the zoom lens.

In this zoom lens, arranging the aperture diaphragm in the rear group is preferable in terms of reducing the diameter of the diaphragm and reducing the size of the diaphragm unit. Arranging the aperture stop in the rear group means that the aperture stop is arranged on the object side or the image side of each lens group constituting the rear group, or in each lens group constituting the rear group. As described above, in the zoom lens, since the second lens group has a relatively large zooming effect, the diameter of the incident light beam with respect to the rear group varies little. Therefore, the diameter of the aperture diaphragm can be made smaller, and in order to suppress fluctuations in the diameter of the aperture, the lens group located closest to the object side of the rear group or the lens group constituting the rear group It is more preferable to place the aperture stop inside.

Further, when the rear group includes the lens surface rn and the lens surface Lnr, the aperture stop is preferably arranged closer to the object side than the lens surface rn and the lens surface Lnr. In order to cancel negative distortion and positive curvature of field generated in the second lens group, it is sufficient to generate aberration in the same direction before and after the aperture stop is interposed. Therefore, when arranging the aperture diaphragm in the rear group, if the aperture diaphragm is arranged on the object side of the surface rn and the lens Lnr, the negative distortion and the positive curvature of field generated in the second lens group can be eliminated in the rear group. can be efficiently canceled, and it is easier to realize a compact zoom lens with high optical performance, which is preferable.

(7) Lens Group Configuration Although the number of lens groups that make up the zoom lens is not particularly limited, for example, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, and a third lens group The following are the six-group zoom lens, which is the rear group having positive refractive power as a whole, the first lens group having positive refractive power, the second lens group having negative refractive power, and the second lens group having positive refractive power. Consists of 3 lens groups, 4th lens group with negative refractive power, 5th lens group with negative refractive power, and 6th lens group with positive refractive power. A six-group zoom lens that is a rear group having power, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a positive refractive power. It consists of a fourth lens group with a positive refractive power, a fifth lens group with a negative refractive power, a sixth lens group with a negative refractive power, and a seventh lens group with a positive refractive power. Various lens group configurations such as a zoom lens having a seven-group configuration, which is a rear group having a positive refractive power, can be employed. If the structure comprises a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear group having positive refractive power as a whole, in order from the object side, the zoom lens A specific lens group configuration is not particularly limited.

1-2. Operation (1) Operation during zooming In the zoom lens, zooming from the wide-angle end to the telephoto end is performed by changing the distance on the optical axis between adjacent lens groups. As long as the distance on the optical axis between the lens groups adjacent to each other changes, the increase or decrease of the distance between the lens groups is not particularly limited. For example, when zooming from the wide-angle end to the telephoto end, the first lens group and the second lens group are relatively arranged so that the distance on the optical axis between the first lens group and the second lens group decreases. If it is moved, it is possible to obtain a compact zoom lens with a high zoom ratio, which is preferable. At this time, the second lens group and the lens group arranged closest to the object side in the rear group are relatively moved so that the distance on the optical axis between the second lens group and the rear group is reduced. is preferable for obtaining a compact zoom lens with a high zoom ratio. In addition, to move the lens groups relatively means to move two lens groups adjacent to each other with an air gap, or to move either one of the two lens groups adjacent to each other with an air gap. It also includes moving groups.

The rear group consists of a plurality of lens groups. As long as the distance on the optical axis between the lens groups constituting the rear group changes during zooming, the increase or decrease of the distance between the lens groups is not particularly limited. Further, when zooming, the lens groups may be moved relative to each other so that the distance between the lens groups forming the rear group on the optical axis changes. It may move along the axis, or any one or more lens groups may be fixed relative to the image plane and the other lens groups move along the optical axis.

When zooming from the wide-angle end to the telephoto end, the direction and amount of movement of each lens group are not particularly limited, and can be appropriately set according to the required zoom ratio. For example, by moving the first lens group closest to the object side in the zoom lens, the overall optical length of the zoom lens at the wide-angle end can be shortened. In this case, the lens barrel has a telescopic structure in which the inner barrel portion is accommodated in the outer barrel portion so that the inner barrel portion can be extended from the wide-angle end to the telephoto end. side so that the inner barrel portion is accommodated in the outer barrel portion during zooming from the telephoto end to the wide-angle end, the length of the lens barrel in the wide-angle end state can be shortened, and the entire zoom lens unit miniaturization can be achieved.

(2) Operation at Focusing When a focus group is provided in the zoom lens, as described above, the position, refractive power, etc. of the focus group are not particularly limited. Also, the direction of movement of the focus group and the like are not particularly limited when focusing on a close object from infinity. For example, when a focus group having negative refractive power is arranged in the rear group, it is preferable to move the focus group toward the image side to focus on a close object from infinity. On the other hand, when the second lens group is used as a focus group, it is preferable to move the second lens group toward the object side to focus on a close object from infinity.

Here, the amount of longitudinal chromatic aberration and the amount of spherical aberration that occur when imaging a close subject is smaller at the wide-angle end than at the telephoto end. Therefore, even if the shortest imaging distance at the wide-angle end is shorter than the shortest imaging distance at the telephoto end, the amount of each aberration generated at the wide-angle end is small. Therefore, by shortening the shortest imaging distance at the wide-angle end with respect to the shortest imaging distance at the telephoto end, it is possible to appropriately select the imaging angle of view according to the distance to the subject and the size of the subject. An imaging scene that can be imaged by the lens can be expanded. However, the shortest imaging distance (shortest shooting distance) means the shortest distance from the imaging plane to the object.

1-3. Conditional Expressions It is preferable that the zoom lens adopts the configuration described above and satisfies one or more of the following conditional expressions.

1-3-1. Conditional expression (1)
0.0000<ΔPgFp1<0.0180 (1)
however,
ΔPgFp1: Anomalous dispersion of the lens having the largest anomalous dispersion among the lenses having positive refractive power included in the first lens group. In the coordinate system with the number νd as the horizontal axis, the coordinates of the glass material C7 with a partial dispersion ratio of 0.5393 and νd of 60.49 and the coordinates of the glass material F2 with a partial dispersion ratio of 0.5829 and νd of 36.30. The deviation from the reference line of the partial dispersion ratio is defined as the straight line passing

The above conditional expression (1) defines the anomalous dispersion of the lens having positive refractive power included in the first lens group. By satisfying conditional expression (1), it is possible to satisfactorily correct chromatic aberration and keep the cost within an appropriate range.

In the lens group with positive refractive power, it is common to correct chromatic aberration by making the lens with negative refractive power made of a high dispersion glass material and making the lens with positive refractive power made of a low dispersion glass material. . However, while the refractive index of a high-dispersion glass material changes in a positive quadratic curve from short to long wavelengths in the visible light region, the refractive index of a low-dispersion glass material changes linearly. Even if two lenses are combined, it is difficult to correct chromatic aberration in all wavelength regions just enough. On the other hand, in a lens made of a glass material having positive anomalous dispersion, the refractive index changes in a positive quadratic curve from a short wavelength to a long wavelength, like a high-dispersion glass material. Therefore, if the lens having positive refractive power is made of a glass material having positive anomalous dispersion, it becomes easy to correct chromatic aberration even in the long wavelength region. preferable. On the other hand, lenses made of glass materials with high anomalous dispersion are expensive. The lenses that make up the first lens group have a larger diameter than the lenses that make up the other lens groups. Therefore, it is not preferable to use a lens made of a glass material with too high anomalous dispersion in the first lens group in order to reduce the cost of the zoom lens. Therefore, if the numerical value of conditional expression (1) is equal to or greater than the upper limit, it is preferable for better correction of chromatic aberration, but it is not preferable because it becomes difficult to reduce costs. Further, if the numerical value of conditional expression (1) is equal to or less than the lower limit, this is preferable in terms of cost reduction, but it is not preferable because correction of chromatic aberration in the long wavelength region tends to be insufficient.

In order to obtain the above effect, the lower limit of conditional expression (1) is more preferably 0.0015, more preferably 0.0018, even more preferably 0.0025, and 0.0030. 0.0045 is even more preferred. Further, the upper limit of conditional expression (1) is more preferably 0.0150, and even more preferably 0.0140.
In the conditional expression (1), preferable numerical values for the above lower limit and upper limit can be selected as appropriate, and in that case, the inequality sign (<) in the conditional expression (1) is converted to an inequality sign with an equal sign (≤). You may The same applies to other conditional expressions.

More preferably, all lenses having positive refractive power in the first lens group satisfy conditional expression (1).

1-3-2. Conditional expression (2)
1.86 < NdL1n < 2.20 (2)
however,
NdL1n: refractive index for the d-line of the lens L1n having negative refractive power included in the first lens group

Conditional expression (2) defines the refractive index for the d-line of the lens L1n having negative refractive power and included in the first lens group. In the lens group having positive refractive power, the Petzval sum can be corrected by making the lens having negative refractive power made of high refractive index glass material and making the lens having positive refractive power made of low refractive index glass material. Common. However, lenses made of a glass material with a high refractive index are expensive. The lenses forming the first lens group have a larger diameter than the other lens groups. Therefore, it is not preferable to use a lens made of a glass material having a too high refractive index for the first lens group in order to reduce the cost of the zoom lens. Satisfying the conditional expression (2) is preferable because the Petzval sum can be corrected satisfactorily, and the cost can be kept within an appropriate range while ensuring good image plane properties.

To obtain these effects, the lower limit of conditional expression (2) is preferably 1.88, more preferably 1.90. The upper limit of conditional expression (2) is preferably 2.10, more preferably 2.05.

1-3-3. Conditional expression (3)
-0.35 < β2w < -0.12 (3)
however,
β2w: lateral magnification at the wide-angle end of the second lens group

Conditional expression (3) is an expression for defining the lateral magnification of the second lens group at the wide-angle end. By satisfying conditional expression (3), the refractive power of the second lens group is within an appropriate range for widening the angle of view at the wide-angle end of the zoom lens, thereby widening the angle of view of the zoom lens, It becomes easy to reduce the cost of the zoom lens.

On the other hand, if the numerical value of conditional expression (3) exceeds the upper limit, the refractive power of the second lens group becomes strong, making it difficult to satisfactorily correct aberrations with a small number of lenses. This is not preferable for cost reduction of the lens. On the other hand, if the numerical value of conditional expression (3) is equal to or less than the lower limit, the refractive power of the second lens group becomes small, which is not preferable for widening the angle of view of the zoom lens.

In order to obtain the above effect, the lower limit of conditional expression (3) is more preferably −0.32, more preferably −0.30, even more preferably −0.28, and − 0.26 is more preferred, and -0.24 is even more preferred. The upper limit of conditional expression (3) is preferably −0.14, more preferably −0.15, even more preferably −0.16, and −0.18. Even more preferable.

1-3-4. Conditional expression (4)
0.002<|ΔA|/RP<0.080 (4)
however,
RP: the maximum effective radius of the aspheric surface ra included in the rear group ΔA: the sag amount of the aspheric surface ra at the height position RP from the optical axis and the paraxial defined by the paraxial radius of curvature of the aspheric surface ra Difference from spherical surface sag amount

Conditional expression (4) is an expression for defining the shape of the object-side convex aspherical surface ra included in the rear group. As described above, the aspheric surface ra preferably has a shape in which the refractive power at its periphery is weaker than the refractive power at the paraxial spherical surface defined by the paraxial radius of curvature. The amount is preferably an amount that satisfies the above conditional expression (4).

By arranging the aspherical surface ra having a shape that satisfies conditional expression (4) in the rear group, it is possible to reduce the amount of spherical aberration and coma while providing strong refractive power to the lens. , a zoom lens with high optical performance can be realized with a small number of lenses.

On the other hand, when the numerical value of conditional expression (4) is equal to or greater than the upper limit, the difference between the sag amount of the aspheric surface ra and the sag amount of the paraxial spherical surface is large, and the refractive power at the peripheral portion of the lens is reduced to the near Since the refracting power is weaker than that on the axial spherical surface, correction of spherical aberration becomes excessive. On the other hand, when the numerical value of conditional expression (4) is equal to or less than the lower limit, the difference between the sag amount of the aspherical surface ra and the sag amount of the paraxial spherical surface is small, and the refractive power at the peripheral portion of the lens and the Since the difference with the refracting power is also small, correction of aspherical aberration and coma is insufficient. Therefore, in either case, it becomes difficult to satisfactorily correct aberrations with a small number of lenses, and it becomes difficult to realize a compact zoom lens with high optical performance at low cost, which is not preferable.

In order to obtain the above effect, the lower limit of conditional expression (4) is more preferably 0.004, more preferably 0.006, even more preferably 0.007, and 0.008. 1 is even more preferred, and 0.010 is even more preferred. The upper limit of conditional expression (4) is preferably 0.070, more preferably 0.050, even more preferably 0.040, and even more preferably 0.030.

1-3-5. Conditional expression (5)
0.20<f2/frn<0.80 (5)
however,
f2: focal length of the second lens group frn: focal length of the lens surface having the largest negative refractive power among the lens surfaces rn included in the rear group

Conditional expression (5) is an expression for defining the ratio between the focal length of the second lens group and the focal length of the surface rn in the rear group having a concave shape toward the image side. When there are a plurality of lens surfaces rn having a concave shape on the image side, the focal length of the lens surface rn having the largest negative refractive power among them is frn. By satisfying the conditional expression (5), the lens surface rn can cancel the negative distortion aberration and the positive curvature of field generated in the second lens group. As a result, it is possible to reduce the amount of distortion aberration and curvature of field while miniaturizing the zoom lens, thereby making it easier to realize a zoom lens with high optical performance. In addition, in order to obtain the effect, it is preferable that the lens surface rn is arranged on the image side of the stop, and the lens surface rn having the largest negative refractive power absolute value among the lens surfaces rn included in the rear group. is arranged closer to the image side than the diaphragm. Assuming that the radius of curvature of the lens surface rn is r, the refractive index on the image side is n', and the refractive index on the object side is n, frn is calculated by frn=r/(n'-n).

In order to obtain the above effect, the lower limit of conditional expression (5) is more preferably 0.22, more preferably 0.25, even more preferably 0.28, and 0.32. It is even more preferable to have The upper limit of conditional expression (5) is preferably 0.75, more preferably 0.70, even more preferably 0.65, even more preferably 0.60, 0.55 is even more preferred.

1-3-6. Conditional expression (6)
2.00<CrL1f/fw<1000.00 (6)
however,
CrL1f: radius of curvature of the lens surface closest to the object side in the first lens group fw: focal length of the zoom lens at the wide-angle end

Conditional expression (6) defines the ratio between the radius of curvature of the lens surface located closest to the object side in the first lens group and the focal length of the zoom lens at the wide-angle end. Satisfying conditional expression (6) is preferable because it is possible to satisfactorily correct distortion and curvature of field, realize a compact zoom lens with high optical performance, and suppress the occurrence of ghosts. .

On the other hand, when the numerical value of conditional expression (6) is equal to or less than the lower limit value, that is, the radius of curvature of the lens surface located closest to the object side in the first lens group with respect to the focal length of the zoom lens at the wide-angle end If is too small, distortion will be overcorrected and field curvature will be difficult to correct, which is not preferable. On the other hand, when the numerical value of conditional expression (6) is equal to or greater than the upper limit, the lens surface located closest to the object side in the first lens group becomes nearly flat, and the light incident on the zoom lens is projected onto the image surface or the cover glass. , and the reflected light is re-reflected by the lens surface located closest to the object side in the first lens group, and re-incidents on the image plane, causing a ghost, which is undesirable. In this case, in order to achieve a predetermined zoom ratio, angle of view, etc., it is necessary to increase the effective diameter of the lens surface located closest to the object side in the first lens group. It is not preferable in terms of

In order to obtain the above effect, the lower limit of conditional expression (6) is more preferably 2.50, more preferably 3.00, even more preferably 3.50, and at 4.00 1 is even more preferred, 4.50 is even more preferred, and 5.50 is even more preferred. The upper limit of conditional expression (6) is preferably 500.00, more preferably 100.00, still more preferably 50.00, and even more preferably 40.00.

1-3-7. Conditional expression (7)
-0.90 < β2t < -0.45 (7)
however,
β2t: Lateral magnification of the second lens group at the telephoto end

Conditional expression (7) defines the lateral magnification of the second lens group at the telephoto end. By satisfying the conditional expression (7), it is possible to realize a zoom lens having a long focal length at the telephoto end and to reduce the cost.

On the other hand, when the numerical value of conditional expression (7) is equal to or less than the lower limit, the lateral magnification of the second lens group at the telephoto end increases, and the magnification of the second lens group increases. It becomes necessary to correct the generated chromatic aberration to be smaller. Therefore, in order to obtain a zoom lens with small chromatic aberration, it is necessary to use a glass material with small dispersion for the lenses constituting the first lens group. Since a glass material with small dispersion is expensive, it is not preferable to reduce the cost of the zoom lens. On the other hand, if the numerical value of conditional expression (7) exceeds the upper limit, the lateral magnification of the second lens group at the telephoto end becomes small, making it difficult to increase the focal length at the telephoto end. Therefore, it is difficult to achieve a high zoom ratio with a standard zoom lens, which is not preferable.

In order to obtain the above effect, the lower limit of conditional expression (7) is more preferably −0.85, more preferably −0.80, and even more preferably −0.75, -0.70 is even more preferred, and -0.65 is even more preferred. The upper limit of conditional expression (7) is preferably −0.47, more preferably −0.48, even more preferably −0.51, and −0.52. Even more preferable.

1-3-8. Conditional expression (8)
1.86<NdLnr<2.20 (8)
however,
NdLnr: Refractive index for the d-line of the lens Lnr, which has the highest refractive index among the lenses having negative refractive power included in the rear group

Conditional expression (8) defines the refractive index for the d-line of the lens Lnr, which has the highest refractive index among the lenses having negative refractive power included in the rear group. Here, the rear group should include at least one lens having negative refractive power, and if there are a plurality of lenses having negative refractive power contained in the rear group, the lens with the highest refractive index among them should be selected. Let the lens be Lnr. Also, a plurality of lenses Lnr may be present in the rear group, and the number of lenses Lnr included in the rear group is not particularly limited. By satisfying the conditional expression (8), the Petzval sum can be well corrected, and a zoom lens with small curvature of field can be realized.

In order to obtain the above effect, the lower limit of conditional expression (8) is preferably 1.88, more preferably 1.90. The upper limit of conditional expression (8) is preferably 2.10, more preferably 2.05.

1-3-9. Conditional expression (9)
0.01<|X1|/ft<0.70 (9)
however,
X1: Distance from the position closest to the image side to the position closest to the object side where the first lens group is positioned during zooming from the wide-angle end to the telephoto end ft: the focal length of the zoom lens at the telephoto end

Conditional expression (9) defines the amount of movement of the first lens group toward the object side when zooming from the wide-angle end to the telephoto end. When conditional expression (9) is satisfied, the refractive power of the first lens group is appropriate, and the amount of movement during zooming is within an appropriate range. Therefore, it is possible to shorten the total optical length of the zoom lens at the wide-angle end while ensuring a predetermined variable magnification, and it is possible to reduce the size of the zoom lens.

On the other hand, when the numerical value of conditional expression (9) is equal to or less than the lower limit, the amount of movement of the first lens group during zooming becomes small. In this case, it is necessary to increase the refractive power of each lens group in order to secure a predetermined zoom ratio. Increasing the refractive power of each lens group requires a large number of lenses for correcting aberrations such as axial chromatic aberration and spherical aberration, making it difficult to reduce the size of the zoom lens. Further, when the numerical value of conditional expression (9) is equal to or greater than the upper limit, the amount of movement of the first lens group during zooming increases. In this case, when the lens barrel has a nested structure in which the inner barrel is accommodated in the outer barrel, if the length of the barrel is designed according to the total optical length at the wide-angle end, the inner barrel is doubled and the outer barrel is This complicates the structure of the lens barrel and increases the outer diameter of the lens barrel, which is not preferable.

However, "the distance from the position closest to the image side of the first lens group to the position closest to the object side during zooming from the wide-angle end to the telephoto end" means "the distance from the position closest to the object side during zooming from the wide-angle end to the telephoto end". It is equal to the distance (difference) on the optical axis between the position closest to the image side at which the first lens group can be positioned and the position closest to the object side at which the first lens group can be positioned. Therefore, "X1" is "the distance between the most image-side position where the first lens group can be positioned and the most object-side position where the first lens group can be positioned during zooming from the wide-angle end to the telephoto end. can be rephrased as "the distance on the optical axis". For example, when zooming from the wide-angle end to the telephoto end, if the first lens group moves toward the object while drawing a convex trajectory toward the image side, the convex trajectory drawn by the first lens group during zooming and the position where the first lens group is closest to the object side (most object side position) at the wide-angle or telephoto end is X1. The trajectory of the movement of the first lens group may be convex toward the image side as described above, may be convex toward the object side, may be S-shaped, and is not particularly limited. not something. Of course, the trajectory of the movement of the first lens group may be a straight line.

In order to obtain the above effect, the lower limit of conditional expression (9) is more preferably 0.05, more preferably 0.10, even more preferably 0.15, and 0.20. It is even more preferable to have The upper limit of conditional expression (9) is more preferably 0.67, still more preferably 0.65, still more preferably 0.62, and even more preferably 0.60.

1-3-10. Conditional expression (10)
0.010<D2rt/ft<0.040 (10)
however,
D2rt: distance on the optical axis between the most image-side lens surface of the second lens group and the most object-side lens surface of the rear group at the telephoto end ft: the focal length of the zoom lens at the telephoto end

Conditional expression (10) defines the distance on the optical axis between the lens surface of the second lens group closest to the image side and the lens surface of the rear group closest to the object side. When the conditional expression (10) is satisfied, the distance between the second lens group and the rear group at the telephoto end is appropriate, the mechanical structure can be simplified, and the overall length can be reduced at the telephoto end. Since the ray height of the rear group can be lowered, the sensitivity of the rear group can be reduced. As a result, aberrations caused by manufacturing errors can be reduced, making it easier to achieve a zoom lens with high optical performance.

On the other hand, when the numerical value of conditional expression (10) is equal to or less than the lower limit, the distance on the optical axis between the second lens group and the rear group at the telephoto end becomes small. If the diaphragm unit is arranged on the object side of the rear group, interference occurs between the second lens group and the diaphragm unit, which makes the mechanical configuration for driving the second lens group and the diaphragm difficult, which is not preferable. Further, when the numerical value of conditional expression (10) exceeds the upper limit, the distance on the optical axis between the second lens group and the rear group at the telephoto end increases. In this case, since the total optical length at the telephoto end becomes long, it becomes difficult to achieve miniaturization. Further, if the distance between the second lens group and the rear group at the telephoto end is large, the height of the light rays incident on the rear group increases. The spherical aberration coefficient is proportional to the cube of the entrance pupil diameter. Therefore, as the height of the ray increases, the amount of various aberrations generated increases. Therefore, as the height of the rays incident on the rear group increases, aberrations caused by manufacturing errors increase, requiring high component precision and ease of assembly, making it difficult to manufacture high-yield zoom lenses with high optical performance. , which is not preferable in terms of cost reduction.

In order to obtain the above effect, the lower limit of conditional expression (10) is more preferably 0.012, more preferably 0.015, even more preferably 0.020, and 0.025. It is even more preferable to have The upper limit of conditional expression (10) is more preferably 0.038, still more preferably 0.035, even more preferably 0.032, and even more preferably 0.030.

1-3-11. Conditional expression (11)
−1.50 < βrw < −0.65 (11)
however,
βrw: Combined lateral magnification of the rear group at the wide-angle end

Conditional expression (11) defines the lateral magnification of the rear group at the wide-angle end. By satisfying conditional expression (11), it is possible to reduce the size of the zoom lens while ensuring a back focus suitable for the interchangeable lens.

On the other hand, if the numerical value of conditional expression (11) is equal to or less than the lower limit value, that is, if the lateral magnification of the rear group at the wide-angle end becomes too large, the back focus at the wide-angle end becomes long. The optical total length of the lens becomes long, which is not preferable in terms of miniaturization. On the other hand, when the numerical value of conditional expression (11) exceeds the upper limit value, that is, when the lateral magnification of the rear group at the wide-angle end becomes too small, the back focus at the wide-angle end becomes short. Since it is difficult to secure the lens, it is not preferable as an interchangeable lens.

In order to obtain the above effect, the lower limit of conditional expression (11) is more preferably −1.30, more preferably −1.20, even more preferably −1.15, and − 1.10 is even more preferable. The upper limit of conditional expression (11) is more preferably −0.70, more preferably −0.75, even more preferably −0.80, and −0.85. Even more preferred, and -0.90 is even more preferred.

1-3-12. Conditional expression (12)
0.50<|(1−βvct)×βvctr|<6.00 (12)
however,
βvct: Lateral magnification of the anti-vibration group at the telephoto end when focused on infinity βvctr: Composite lateral magnification of all lenses arranged closer to the image side than the anti-vibration group at the telephoto end when focused on infinity

Conditional expression (12) is an expression for defining the so-called blur correction coefficient of the anti-vibration group. Here, the blur correction coefficient represents the amount of movement of the imaging plane when the anti-vibration group moves by a unit amount in a direction substantially perpendicular to the optical axis. By satisfying conditional expression (12), the amount of movement of the anti-vibration group during image blur correction can be kept within an appropriate range, realizing high-precision and rapid image blur correction, as well as the zoom lens. It becomes easy to achieve miniaturization.

On the other hand, if the numerical value of conditional expression (12) is equal to or less than the lower limit, the blur correction coefficient becomes too small. As a result, the amount of movement of the anti-vibration group during anti-vibration increases and the outer diameter of the anti-vibration unit increases, making it difficult to downsize the zoom lens, which is undesirable. Further, when the numerical value of conditional expression (12) exceeds the upper limit, the blur correction coefficient becomes too large. As a result, the amount of movement of the anti-vibration group for correcting the image shift becomes too small, and the position of the anti-vibration group must be controlled with high precision during image stabilization.

In order to obtain the above effect, the lower limit of conditional expression (12) is more preferably 0.60, more preferably 0.70, even more preferably 0.85, and at 1.00 1 is even more preferred, and 1.10 is even more preferred. The upper limit of conditional expression (12) is more preferably 5.00, more preferably 4.10, even more preferably 3.00, and even more preferably 2.30. , 2.20.

1-3-13. Conditional expression (13)
0.40<f1/ft<1.20 (13)
however,
f1: focal length of the first lens group ft: focal length of the zoom lens at the telephoto end

Conditional expression (13) is an expression for defining the ratio between the focal length of the first lens group and the focal length of the zoom lens at the telephoto end. By satisfying conditional expression (13), the refractive power of the first lens group falls within an appropriate range, and it becomes easy to realize a compact zoom lens with high optical performance.

On the other hand, if the numerical value of conditional expression (13) falls below the lower limit, the refractive power of the first lens group becomes too large. As a result, spherical aberration and curvature of field occur at the telephoto end, making it difficult to obtain a zoom lens with high optical performance, which is undesirable. Further, when the numerical value of conditional expression (13) exceeds the upper limit, the refractive power of the first lens group becomes too small. As a result, the total optical length at the telephoto end becomes long, which is not preferable for miniaturization of the zoom lens.

In order to obtain the above effect, the lower limit of conditional expression (13) is more preferably 0.45, more preferably 0.48, even more preferably 0.50, and at 0.55 1 is even more preferred, and 0.60 is even more preferred. Further, the upper limit of conditional expression (13) is more preferably 1.15, more preferably 1.10, even more preferably 1.05, and even more preferably 1.00. , 0.98.

1-3-14. Conditional expression (14)
-1.50 < f2/fw < -0.50 (14)
however,
f2: focal length of the second lens group fw: focal length of the zoom lens at the wide-angle end

Conditional expression (14) is an expression for defining 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 (14), the refractive power of the second lens group can be kept within an appropriate range, and it becomes easy to realize a compact zoom lens with high optical performance.

On the other hand, if the numerical value of conditional expression (14) is less than the lower limit, the refractive power of the second lens group becomes too small, making it difficult to position the entrance pupil on the object side. This is not preferable because it becomes difficult to reduce the diameter of the lenses constituting one lens group. Further, when the numerical value of conditional expression (14) exceeds the upper limit, the refractive power of the second lens group becomes too large. As a result, curvature of field and distortion are overcorrected, making it difficult to realize a zoom lens with high optical performance, which is not preferable.

In order to obtain the above effects, the lower limit of conditional expression (14) is more preferably −1.40, more preferably −1.30, even more preferably −1.20, and − 1.10 is even more preferred, and -1.00 is even more preferred. The upper limit of conditional expression (14) is more preferably −0.52, more preferably −0.55, even more preferably −0.58, and −0.62. is even more preferred, -0.65 is even more preferred, and -0.70 is even more preferred.

1-13-15. Conditional expression (15)
0.80<D2rw/fw<2.00 (15)
however,
D2rw: Distance on the optical axis between the most image-side lens surface of the second lens group and the most object-side lens surface of the rear group at the wide-angle end fw: Focal length of the zoom lens at the wide-angle end

Conditional expression (15) is the distance on the optical axis between the lens surface of the second lens group closest to the image side and the lens surface of the rear group closest to the object at the wide-angle end, and the zoom lens is a formula that defines the ratio of the focal length of . When conditional expression (15) is satisfied, the distance between the second lens group and the rear group at the wide-angle end becomes appropriate, and the size of the zoom lens in the direction of the overall optical length and the diameter of the front lens at the wide-angle end are simultaneously achieved. can be realized.

On the other hand, when the numerical value of conditional expression (15) is equal to or less than the lower limit, the distance between the second lens group and the rear group becomes narrow at the wide-angle end. This zoom lens achieves a zooming action by changing the distance between the second lens group and the rear group. Therefore, if the distance between the second lens group and the rear group is narrow at the wide-angle end, it becomes difficult to increase the zoom ratio, making it difficult to realize a zoom lens with a high zoom ratio, which is not preferable. Further, when the numerical value of conditional expression (15) exceeds the upper limit, the distance between the second lens group and the rear group increases at the wide-angle end. In this case, the total optical length at the wide-angle end becomes longer, which is not preferable in terms of miniaturization of the zoom lens in the direction of the total optical length. In addition, when the distance between the second lens group and the rear group increases at the wide-angle end, it becomes difficult to place the entrance pupil on the object side when an aperture diaphragm is arranged in the rear group. will move to As a result, the diameter of the front lens becomes large, which is not preferable for reducing the size of the zoom lens in the radial direction. Further, as the diameter of the front lens increases, the cost of the lens increases, which is not preferable in terms of reducing the cost of the zoom lens.

In order to obtain the above effect, the lower limit of conditional expression (15) is more preferably 0.90, more preferably 0.95, even more preferably 1.00, and 1.05. 1 is even more preferred, and 1.10 is even more preferred. The upper limit of conditional expression (15) is more preferably 1.90, more preferably 1.80, even more preferably 1.70, and even more preferably 1.60. .

2. Imaging Apparatus Next, an imaging apparatus according to the present invention will be described. An imaging device according to the present invention includes the zoom lens according to the present invention, and an imaging device provided on the image plane side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal. characterized by

Here, the imaging element or the like is not particularly limited, and a solid-state imaging element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The imaging device according to the present invention is suitable for imaging devices using these solid-state imaging devices, such as digital cameras and video cameras. Further, the imaging device may be a lens-fixed imaging device in which a lens is fixed to a housing, or may be a lens-exchangeable imaging device such as a single-lens reflex camera or a mirrorless single-lens camera. is of course. In particular, the zoom lens according to the present invention can ensure a suitable back focus for interchangeable lens systems. Therefore, it is suitable for an imaging device such as a single-lens reflex camera equipped with an optical finder, a phase difference sensor, and a reflex mirror for branching light to these.

The imaging apparatus includes an image processing unit that electrically processes captured image data acquired by a solid-state imaging device to change the shape of the captured image, and an image correction that is used to process the captured image data in the image processing unit. It is more preferable to have an image correction data holding section for holding data, an image correction program, and the like. When the size of the zoom lens is reduced, the shape of the picked-up image formed on the imaging plane is likely to be distorted. At this time, the distortion correction data for correcting the distortion of the captured image shape is stored in advance in the image correction data storage unit, and the image processing unit uses the distortion correction data stored in the image correction data storage unit. , it is preferable to correct the distortion of the captured image shape. 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.

Further, in the image pickup apparatus according to the present invention, the image correction data holding unit holds the magnification chromatic aberration correction data in advance, and the image processing unit uses the magnification chromatic aberration correction data held in the image correction data holding unit. , it is preferable to correct the chromatic aberration of magnification of the captured image. By correcting lateral chromatic aberration, that is, color distortion aberration, the image processing unit can 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.

EXAMPLES Next, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following examples.

(1) Optical Configuration of Zoom Lens FIG. 1 is a cross-sectional view of the lens configuration of the zoom lens according to Example 1 of the present invention when focusing on infinity at the wide-angle end. The zoom lens includes, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having negative refractive power, and a positive lens group G3. A fourth lens group G4 having a refractive power of , a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a positive refractive power. Magnification is performed by changing the interval. An aperture stop S is arranged on the object side of the third lens group G3. In this embodiment, the rear group consists of a third lens group G3, a fourth lens group G4, a fifth lens group G5 and a sixth lens group G6.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens in which an object-side convex negative meniscus lens L1 and a convex lens L2 are cemented together, and an object-side convex positive meniscus lens L3. The object-side convex negative meniscus lens L1 is the lens L1n referred to in the present invention. Among the lenses having positive refractive power included in the first lens group, the lens with the highest anomalous dispersion is the lens L2. ΔPgFp1 of lens L2 is 0.009.

The second lens group G2 is composed of, in order from the object side, an object side convex negative meniscus lens L4, a biconcave lens L5, a biconvex lens L6, and an object side concave negative meniscus lens L7. All lens surfaces included in the second lens group are spherical.

The third lens group G3 includes, in order from the object side, an aperture diaphragm S, a biconvex lens L8, a cemented lens in which a biconvex lens L9 and a concave lens L10 are cemented together, a biconcave lens L11, and a positive meniscus lens L12 convex on the object side. It is composed of a cemented cemented lens. The concave lens L10 is a lens Lnr having a negative refractive power included in the rear group referred to in the present invention.

The fourth lens group G4 is composed of, in order from the object side, a double convex positive lens L13 having aspherical surfaces on both sides, and a cemented lens in which a double convex lens L14 and a concave lens L15 are cemented together. The object surface of the positive lens L13 is an aspherical surface ra convex to the object side referred to in the present invention.

The fifth lens group G5 is composed of an object side convex negative meniscus lens L16. The image side surface of the negative meniscus lens L16 is the lens surface rn having a concave shape toward the image side referred to in the present invention.

The sixth lens group G6 is composed of a positive meniscus lens L17 having a concave shape on the object side.

In the zoom lens of Example 1, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the object side, and the third lens group G2 moves toward the object side with respect to the image plane. The group G3 moves to the object side, the fourth lens group G4 moves to the object side, the fifth lens group G5 moves to the object side, and the sixth lens group G6 is fixed in the optical axis direction.

If the group having negative refractive power in the rear group makes a U-turn toward the image side with respect to the group on the object side, the image plane property at the intermediate focal length is improved. In this embodiment, the fifth lens group G5 corresponds to the group having negative refractive power among the rear groups. During focusing from an infinity object to a close object, the fifth lens group G5 moves along the optical axis toward the image side.

In addition, in order to correct image blur caused by vibration transmitted to the imaging device during shooting due to so-called camera shake, etc., the image is shifted by decentering at least one lens included in the optical system. It is preferable to provide an anti-vibration group. In this embodiment, for example, a cemented lens composed of a biconcave lens L11 and an object-side convex positive meniscus lens L12 included in the third lens group can serve as a vibration reduction group. It is preferable to shift the image when image blurring occurs by moving in the direction perpendicular to the axis.

Further, "IMG" shown in FIG. 1 is an imaging plane, and specifically represents an imaging plane of a solid-state imaging device such as a CCD sensor or a CMOS sensor, or a film plane of a silver salt film. A parallel flat plate having no substantial refractive power, such as a cover glass CG, is provided on the object side of the imaging plane IMG. Since these points are the same in each lens cross-sectional view shown in other examples, description thereof will be omitted below.

(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. In Table 1, "surface number" is the order of the lens surfaces counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the distance between the lens surfaces on the optical axis, and "Nd" is the d-line (wavelength λ = 587.6 nm), "νd" is the Abbe number for the d-line, "H" is the effective radius, and "ΔPgf" is the anomalous dispersion of the lens with positive refractive power included in the first lens group. showing. "ASP" displayed in the column next to the surface number indicates that the lens surface is aspherical, and "S" indicates the aperture stop. Furthermore, "D6", "D14", etc. in the column of the distance between the lens surfaces on the optical axis are variable distances that change the distance between the lens surfaces on the optical axis during zooming or focusing. means that The unit of length in each table is all "mm", and the unit of angle of view is "°". Also, the radius of curvature "0" means a flat surface. The 36th and 37th surfaces in Table 1 are the surface data of the cover glass CG.

Table 2 is a specification table of the zoom lens. The specification table shows the focal length "f", the F number "Fno", the half angle of view "ω", the image height "Y", and the total optical length "TL" of the zoom lens when focused on infinity. However, Table 2 shows respective values at the wide-angle end, the intermediate focal length state, and the telephoto end in order from the left.

Table 3 shows the variable spacing on the optical axis of the zoom lens during zooming. Table 3 shows, in order from the left, the values at the wide-angle end, the intermediate focal length state, and the infinity focus at the telephoto end. "INF" in the table indicates "∞ (infinity)".

Table 4 shows the variable spacing of the zoom lens on the optical axis during focusing. Table 4 shows values at the wide-angle end, the intermediate focal length state, and the telephoto end when the photographing distance (imaging distance) is 350.00 mm, 700.00 mm, and 1000.00 mm, respectively. These photographing distances are the shortest photographing distances at each focal length.

Table 5 shows the focal length of each lens group that constitutes the zoom lens.

Table 6 shows the aspheric coefficients of each aspheric surface. The aspherical surface coefficient is a value when each aspherical surface shape is defined by the following equation. Also, Table 19 shows the values of each conditional expression (1) to conditional expression (15). Furthermore, Table 20 shows the values used in the calculations of conditional expressions (1) to (15).

X(Y)= ^CY2 /[1+{1-( ¹ +Κ)・^C2Y2 } ^1/2 ]+A4・^Y4 +A6・^Y6 +A8・^Y8 +A10・^Y10 + A12・^Y12

However, in Table 6, "Ea" indicates "×10 ^-a ". In the above formula, "X" is the amount of displacement from the reference plane in the direction of the optical axis, "C" is the curvature at the surface vertex, "Y" is the height from the optical axis in the direction perpendicular to the optical axis, " K” is the conic coefficient, and “An” is the n-th order aspheric coefficient.
Matters related to these tables are the same for each table shown in other embodiments, so the description is omitted below.

[Table 1]
Surface number rd Nd vd H ΔPgf
1 116.0437 1.370 1.90440 31.31 25.800
2 62.1234 0.020 1.56766 42.84 25.075
3 62.1234 7.089 1.48767 70.44 25.073 0.009
4 -660.0622 0.140 24.903
5 56.5319 5.330 1.59373 67.00 23.700 0.009
6 366.6100 D6 23.476
7 73.1105 0.950 1.91149 35.25 12.848
8 14.8677 5.720 10.171
9 -52.3595 0.830 1.77291 49.62 9.772
10 35.8574 0.167 9.272
11 24.1476 4.502 1.84756 23.78 9.200
12 -36.9502 0.547 8.902
13 -28.1911 0.830 1.77291 49.62 8.715
14 98.7836 D14 8.299
15S 0.0000 1.060 5.620
16 67.4001 2.350 1.48767 70.44 5.874
17 -1195.1709 0.575 6.083
18 24.0699 3.493 1.48767 70.44 6.303
19 -21.1357 0.010 1.56766 42.84 6.323
20 -21.1357 0.800 1.90440 31.31 6.324
21 -114.9128 3.030 6.450
22 -33.7527 0.890 1.59373 67.00 6.841
23 24.6903 0.010 1.56766 42.84 7.139
24 24.6903 1.645 1.80598 25.46 7.140
25 69.5662 D25 7.200
26 ASPs 28.8941 4.008 1.59225 67.02 8.752
27 ASPs -23.1730 0.115 8.820
28 93.5454 3.774 1.48767 70.44 8.878
29 -20.7679 0.010 1.56766 42.84 8.860
30 -20.7679 0.800 1.80598 25.46 8.860
31 -50.5655 D31 9.000
32 65.1102 0.800 1.48767 70.44 8.940
33 20.2552 D33 8.815
34 -4405.2863 1.770 1.52297 68.02 12.218
35 -151.9757 35.111 12.303
36 0.0000 2.000 1.51654 64.14 14.385
37 0.0000 1.000 14.462

[Table 2]
f 18.442 54.706 103.541
Fno 3.728 5.123 5.718
ω 39.955 14.433 7.706
Y 14.500 14.500 14.500
TL 128.620 161.607 185.651

[Table 3]
f 18.442 54.706 103.541
Shooting distance INF INF INF
D6 1.441 25.922 45.260
D14 19.916 5.298 2.680
D25 7.051 5.066 4.154
D31 1.342 4.283 2.719
D33 8.125 30.295 40.094

[Table 4]
f 18.442 54.706 103.541
Shooting distance 350.00 700.00 1000.00
D31 2.065 5.878 5.798
D33 7.402 28.700 37.015

[Table 5]
Group surface number Focal length
G1 1-6 93.429
G2 7-14 -14.876
G3 15-25-957.373
G4 26-31 20.044
G5 32-33-60.645
G6 34-35 300.939

[Table 6]
Plane number 26 27
K 0 0
A4 -2.32531E-05 1.17829E-05
A6 2.43229E-08 3.34264E-09
A8 1.06408E-10 1.47429E-10
A10 0.00000E+00 0.00000E+00
A12 0.00000E+00 0.00000E+00

2 to 4 show longitudinal aberration diagrams of the zoom lens of Example 1 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity. The longitudinal aberration diagrams shown in each figure are spherical aberration (mm), astigmatism (mm), and distortion (%) in order from the left side of the drawing. In the figure representing spherical aberration, the vertical axis is the ratio to the maximum F-number, and the horizontal axis is defocus. ), and the dotted line indicates the spherical aberration at the C line (wavelength λ=656.3 nm). In the diagrams representing astigmatism, the vertical axis represents image height and the horizontal axis represents defocus, the solid line indicates the sagittal image plane (ds) for the d-line, and the dotted line indicates the meridional image plane (dm) for the d-line. In the diagrams representing distortion, the vertical axis represents image height and the horizontal axis represents %. Matters relating to these longitudinal aberration diagrams are the same for the longitudinal aberration diagrams shown in other examples, and therefore description thereof will be omitted below.

Also, the back focus "fb" at the wide-angle end of the zoom lens when focusing on infinity is as follows. However, the following values are values that do not include the cover glass (Nd=1.5168), and the same applies to back focal lengths shown in other examples.
fb = 37.430 (mm)

(1) Optical Configuration of Zoom Lens FIG. 5 is a cross-sectional view of the lens configuration of the zoom lens according to Example 2 of the present invention when focusing on infinity at the wide-angle end. The zoom lens includes, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a positive lens group G3. a fourth lens group G4 having a refractive power of , a fifth lens group G5 having a negative refractive power, a sixth lens group G6 having a negative refractive power, and a seventh lens group G7 having a positive refractive power and performs zooming by changing the distance on the optical axis between adjacent lens groups. The aperture stop S is arranged closest to the image side of the third lens group G3. In this embodiment, the rear group consists of a third lens group G3, a fourth lens group G4, a fifth lens group G5, a sixth lens group G6 and a seventh lens group G7.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens in which an object-side convex negative meniscus lens L1 and a convex lens L2 are cemented together, and an object-side convex positive meniscus lens L3. The object-side convex negative meniscus lens L1 is the lens L1n referred to in the present invention. Among the lenses having positive refractive power included in the first lens group, the lens with the highest anomalous dispersion is the lens L2. ΔPgFp1 of lens L2 is 0.012.

The second lens group G2 is composed of, in order from the object side, an object-side convex negative meniscus lens L4, a biconcave lens L5, a biconvex lens L6, and a biconcave lens L7. All lens surfaces included in the second lens group are spherical.

The third lens group G3 includes, in order from the object side, an aperture diaphragm S, a biconvex lens L8, a cemented lens in which a biconvex lens L9 and a biconcave lens L10 are cemented together, a biconcave lens L11, and a positive meniscus lens L12 convex on the object side. is composed of a cemented lens to which is cemented. The biconcave lens L10 is a lens Lnr having a negative refractive power included in the rear group referred to in the present invention. The biconcave lens L11 is a composite aspherical surface in which an aspherical surface is formed in a composite layer on the object side surface.

The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L13 having aspheric surfaces on both sides, and a biconvex lens L14. The object surface of the positive lens L13 is an aspherical surface ra convex to the object side referred to in the present invention.

The fifth lens group G5 is composed of a cemented lens in which a convex lens L15 and a biconcave lens L16 are cemented together. A lens surface rn having a concave shape on the image side of the biconcave lens L16.

The sixth lens group G6 is composed of a concave lens L17 having a concave surface facing the object side and having aspherical surfaces on both surfaces.

The seventh lens group G7 is composed of a positive meniscus lens L17 having a concave shape on the object side.

In the zoom lens of Example 2, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side with respect to the image plane, and the second lens group G2 moves toward the image side so as to make a U-turn. Then, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, the sixth lens group G6 moves toward the object side, The seventh lens group G7 is fixed in the optical axis direction. The fourth lens group G4 and the sixth lens group G6 move along the same cam locus. Therefore, it is possible to form a connection unit that connects the fourth lens group G4 and the sixth lens group G6 and moves the fourth lens group G4 and the sixth lens group G6 integrally during zooming. As a result, it is possible to reduce the number of cam grooves formed in the lens barrel, which is preferable because the cost can be reduced. Further, even if play due to eccentricity occurs in the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6, the fourth lens group G4 having a positive refractive power and the third lens group G4 having a negative refractive power can be used. Since the six lens groups G6 are decentered at the same time, the aberration caused by the decentration can be canceled by the fourth lens group G4 having positive refractive power and the sixth lens group G6 having negative refractive power. Therefore, it is preferable for realizing high optical performance because the occurrence of aberration during eccentricity is reduced.

It should be noted that when the lens group having negative refractive power in the rear group is moved with respect to the lens group on the object side in such a locus as to make a U-turn toward the image side during zooming, the image plane property of the intermediate focal length is changed. improves. In this embodiment, by moving the fifth lens group G5 along a locus such that it makes a U-turn toward the image side with respect to the lens group on the object side during zooming, it is possible to improve the image plane property at the intermediate focal length. can. During focusing from an infinity object to a close object, the fifth lens group G5 moves along the optical axis toward the image side.

In addition, in order to correct image blur caused by vibration transmitted to the imaging device during shooting due to so-called camera shake, etc., the image is shifted by decentering at least one lens included in the optical system. It is preferable to provide an anti-vibration group. In this embodiment, for example, a cemented lens composed of a biconcave lens L11 and an object-side convex positive meniscus lens L12 included in the third lens group can serve as a vibration reduction group. It is preferable to shift the image when image blurring occurs by moving in the direction perpendicular to the axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 7 shows the surface data of the zoom lens, and Table 8 shows the specifications of the zoom lens. The 35th and 36th surfaces in Table 7 are the surface data of the cover glass CG.

Table 9 shows the variable distance on the optical axis of the zoom lens during zooming, and Table 10 shows the variable distance on the optical axis of the zoom lens during focusing. Note that Table 10 shows the values at the wide-angle end, intermediate focal length state, and telephoto end when the photographing distance (imaging distance) is 180.00 mm, 500.00 mm, and 800.00 mm, respectively. These photographing distances are the shortest photographing distances at each focal length.

Table 11 shows the focal length of each lens group that constitutes the zoom lens. Table 12 shows the aspheric coefficients of each aspheric surface. Also, Table 19 shows the values of each conditional expression (1) to conditional expression (15). Furthermore, Table 20 shows the values used in the calculations of conditional expressions (1) to (15).

6 to 8 show longitudinal aberration diagrams of the zoom lens of Example 2 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity.

Furthermore, the back focus at the wide-angle end of the zoom lens when focusing on infinity is as follows.
fb = 18.321 (mm)

[Table 7]
Surface number rd Nd vd H ΔPgf
1 153.2090 1.200 1.95375 32.32 26.500
2 68.3153 7.068 1.59522 67.73 25.597 0.012
3 -600.5587 0.150 25.398
4 57.2023 5.575 1.59349 67.00 24.000 0.009
5 241.1147 D5 23.679
6 104.5158 1.000 1.78800 47.37 14.286
7 14.6636 6.452 10.922
8 -44.6390 0.800 1.85150 40.78 10.818
9 78.0418 0.150 10.567
10 28.5349 4.953 1.84666 23.78 10.500
11 -41.7440 1.000 10.236
12 -28.8063 0.800 1.78800 47.37 9.909
13 133.4564 D13 9.594
14S 0.0000 1.083 6.840
15 26.9286 3.500 1.80000 29.84 7.305
16 -82.2538 0.278 7.288
17 20.3460 3.391 1.49700 81.61 7.128
18 -37.5335 0.700 1.92286 20.88 6.868
19 39.2815 2.300 6.692
20 ASPs -121.7485 0.225 1.51460 49.96 7.200
21 -90.3447 0.800 1.83481 42.74 7.191
22 29.2450 2.030 1.74077 27.79 7.246
23 57.8928 D23 7.314
24 ASPs 48.5768 2.501 1.53446 57.04 6.980
25 ASPs -91.6865 0.205 7.173
26 40.4588 3.612 1.49700 81.61 7.300
27 -19.9444 D27 7.445
28 -4537.3387 2.231 1.80610 33.27 7.160
29 -24.6840 0.700 1.74320 49.34 7.164
30 25.5037 D30 7.143
31 ASPs -45.1511 1.100 1.53446 57.04 8.922
32 ASP-2771.7000 D32 9.311
33 -143.5306 3.200 1.72916 54.68 14.369
34 -43.2728 16.002 14.573
35 0.0000 2.000 1.51680 64.20 14.518
36 0.0000 1.000 14.532

[Table 8]
f 18.495 78.000 194.355
Fno 3.606 5.429 6.486
ω 40.246 10.184 4.182
Y 14.500 14.500 14.500
TL 122.371 160.089 189.958

[Table 9]
f 18.495 78.000 194.355
Shooting distance INF INF INF
D5 0.819 37.322 58.898
D13 27.549 7.547 2.272
D23 3.823 1.562 1.268
D27 1.295 6.171 3.549
D30 10.713 5.837 8.458
D32 2.166 25.644 39.506

[Table 10]
f 18.495 78.000 194.355
Shooting distance 180.00 500.00 800.00
D27 2.826 9.023 9.815
D30 9.182 2.985 2.193

[Table 11]
Group surface number Focal length
G1 1-5 100.685
G2 6-13 -15.380
G3 14-23 53.493
G4 24-27 19.453
G5 28-30-37.386
G6 31-32-85.891
G7 33-34 83.833

[Table 12]
Plane number 20 24 25 31 32
K 74.6651 0 -89.5392 0 0
A4 2.00436E-05 -6.62844E-05 -1.39417E-06 -1.59331E-05 0.00000E+00
A6 -9.61273E-08 -7.46055E-07 -5.95505E-07 3.09124E-07 1.37942E-07
A8 1.54884E-09 1.37140E-08 1.15035E-08 -3.81395E-09 5.08209E-10
A10 1.60756E-12 -1.73244E-10 -1.19369E-10 5.67643E-11 0.00000E+00
A12 -1.47964E-13 7.75951E-13 4.13378E-13 -2.42231E-13 0.00000E+00

(1) Optical Configuration of Zoom Lens FIG. 9 is a cross-sectional view of the lens configuration of the zoom lens according to Example 3 of the present invention when focusing on infinity at the wide-angle end. The zoom lens includes, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a negative refractive power. A fourth lens group G4 having a refractive power of , a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a positive refractive power. Magnification is performed by changing the interval. An aperture stop S is arranged on the object side of the third lens group G3. In this embodiment, the rear group consists of a third lens group G3, a fourth lens group G4, a fifth lens group G5 and a sixth lens group G6.

The configuration of each lens group will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens in which an object-side convex negative meniscus lens L1 and a convex lens L2 are cemented together, and an object-side convex positive meniscus lens L3. The object-side convex negative meniscus lens L1 is the lens L1n referred to in the present invention. Among the lenses having positive refractive power included in the first lens group, the lens with the highest anomalous dispersion is the lens L2. ΔPgFp1 of lens L3 is 0.012.

The second lens group G2 is composed of, in order from the object side, an object side convex negative meniscus lens L4, a biconcave lens L5, a biconvex lens L6, and an object side concave negative meniscus lens L7. All lens surfaces included in the second lens group are spherical.

The third lens group G3 includes, in order from the object side, an aperture diaphragm S, a biconvex lens L8, a cemented lens in which a biconvex lens L9 and a concave lens L10 are cemented together, a biconcave lens L11, and a positive meniscus lens L12 convex on the object side. It is composed of a cemented cemented lens, a biconvex positive lens L13 having aspherical surfaces on both sides, and a cemented lens in which a biconvex lens L14 and a concave lens L15 are cemented together. The concave lens L10 is a lens Lnr having a negative refractive power included in the rear group referred to in the present invention. The object surface of the positive lens L13 is an aspherical surface ra convex to the object side referred to in the present invention.

The fourth lens group G4 is composed of an object side convex negative meniscus lens L16. The image side surface of the negative meniscus lens L16 is the lens surface rn having a concave shape toward the image side referred to in the present invention.

The fifth lens group G5 is composed of a negative meniscus lens L17 having a concave shape on the object side.

The sixth lens group G6 is composed of a positive meniscus lens L18 having a concave shape on the object side.

In the zoom lens of Example 3, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the object side, and the third lens group G2 moves toward the object side with respect to the image plane. The group G3 moves to the object side, the fourth lens group G4 moves to the object side, the fifth lens group G5 moves to the object side, and the sixth lens group G6 is fixed in the optical axis direction. The third lens group G3 and the fifth lens group G5 move along the same cam locus. Therefore, it is possible to form a connection unit that connects the third lens group G3 and the fifth lens group G5 and moves the third lens group G3 and the fifth lens group G5 integrally during zooming. As a result, it is possible to reduce the number of cam grooves formed in the lens barrel, which is preferable because the cost can be reduced. Further, even if play due to eccentricity occurs in the third lens group G3, the fourth lens group G4 and the fifth lens group G5, the third lens group G3 having a positive refractive power and the third lens group G3 having a negative refractive power Since the five lens groups G5 are decentered at the same time, the third lens group G3 having a positive refractive power and the fifth lens group G5 having a negative refractive power can cancel the aberration caused by the decentering. Therefore, it is preferable for realizing high optical performance because the occurrence of aberration during eccentricity is reduced.

It should be noted that when the lens group having negative refractive power in the rear group is moved with respect to the lens group on the object side in such a locus as to make a U-turn toward the image side during zooming, the image plane property of the intermediate focal length is changed. improves. In this embodiment, by moving the fourth lens group G4 along a locus such that it makes a U-turn toward the image side with respect to the lens group on the object side during zooming, it is possible to improve the image plane property at the intermediate focal length. can. During focusing from an infinity object to a close object, the fourth lens group G4 moves along the optical axis toward the image side.

In addition, in order to correct image blur caused by vibration transmitted to the imaging device during shooting due to so-called camera shake, etc., the image is shifted by decentering at least one lens included in the optical system. It is preferable to provide an anti-vibration group. In this embodiment, for example, a cemented lens composed of a biconcave lens L11 and an object-side convex positive meniscus lens L12 included in the third lens group can serve as a vibration reduction group. It is preferable to shift the image when image blurring occurs by moving in the direction perpendicular to the axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 13 shows the surface data of the zoom lens, and Table 14 shows the specifications of the zoom lens. The 35th and 36th surfaces in Table 13 are the surface data of the cover glass CG.

Table 15 shows the variable spacing on the optical axis of the zoom lens during zooming, and Table 16 shows the variable spacing on the optical axis of the zoom lens during focusing. Note that Table 16 shows the values at the wide-angle end, intermediate focal length state, and telephoto end when the photographing distance (imaging distance) is 350.00 mm, 700.00 mm, and 1000.00 mm, respectively. These photographing distances are the shortest photographing distances at each focal length.

Table 17 shows the focal length of each lens group that constitutes the zoom lens. Table 18 shows the aspheric coefficients of each aspheric surface. Also, Table 19 shows the values of each conditional expression (1) to conditional expression (15). Furthermore, Table 20 shows the values used in the calculations of conditional expressions (1) to (15).

10 to 12 show longitudinal aberration diagrams of the zoom lens of Example 3 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity.

Furthermore, the back focus at the wide-angle end of the zoom lens when focusing on infinity is as follows.
fb = 36.625 (mm)

[Table 13]
Surface number rd Nd vd H ΔPgf
1 104.8965 1.280 1.90440 31.31 26.550
2 57.3143 0.020 1.56766 42.84 25.761
3 57.3143 7.020 1.48767 70.44 25.759 0.009
4 -555.7699 0.120 25.723
5 52.5924 5.116 1.59545 67.73 24.400 0.012
6 310.6774 D6 24.380
7 79.6261 0.900 1.91149 35.25 12.074
8 13.1027 5.711 9.348
9 -35.7503 0.850 1.77291 49.62 9.058
10 37.6675 0.210 8.715
11 23.0886 4.163 1.84756 23.78 8.700
12 -37.6736 0.802 8.485
13 -22.7259 0.840 1.77291 49.62 8.395
14-112.9083 D14 8.238
15S 0.0000 1.000 5.520
16 32.0038 2.160 1.48767 70.44 5.793
17 -95.1737 0.216 5.877
18 135.9561 3.060 1.48767 70.44 5.908
19 -16.9676 0.010 1.56766 42.84 5.958
20 -16.9676 0.800 1.90440 31.31 5.959
21 -47.6458 2.660 6.114
22 -44.5308 0.820 1.59373 67.00 6.550
23 17.6204 0.010 1.56766 42.84 6.939
24 17.6204 1.625 1.80598 25.46 6.941
25 39.4500 3.899 7.000
26 ASPs 25.9009 3.859 1.59225 67.02 7.929
27 ASPs -23.3961 0.211 8.000
28 110.2271 3.676 1.48767 70.44 8.062
29 -15.8153 0.010 1.56766 42.84 8.057
30 -15.8153 0.800 1.80598 25.46 8.058
31 -35.6427 D31 8.259
32 48.2907 0.800 1.48767 70.44 8.218
33 16.6445 D33 8.077
34 -45.0789 0.820 1.52866 54.93 8.901
35 -55.6892 D35 9.084
36 -45.8253 2.131 1.59213 68.78 12.976
37 -30.2466 34.306 13.170
38 0.0000 2.000 1.51654 64.14 14.451
39 0.0000 1.000 14.496

[Table 14]
f 18.508 52.666 104.128
Fno 4.089 5.496 5.791
ω 40.739 15.000 7.706
Y 14.500 14.500 14.500
TL 123.965 161.274 182.641

[Table 15]
f 18.508 52.666 104.128
Shooting distance INF INF INF
D6 1.343 24.902 44.256
D14 20.252 6.633 2.721
D31 1.079 2.805 1.456
D33 7.520 5.794 7.188
D35 0.866 28.234 34.115

[Table 16]
f 18.508 52.666 104.128
Shooting distance 350.00 700.00 1000.00
D31 1.706 4.036 4.102
D33 6.893 4.563 4.541

[Table 17]
Group surface number Focal length
G1 1-6 85.996
G2 7-14 -14.105
G3 15-31 22.260
G4 32-33-52.517
G5 34-35-459.841
G6 36-37 142.982

[Table 18]
Plane number 26 27
K 0 0
A4 -1.63296E-05 1.62919E-05
A6 -1.64690E-07 -1.67925E-07
A8 3.24463E-09 2.65396E-09
A10 -1.35610E-11 -9.31375E-12
A12 0.00000E+00 0.00000E+00

[Table 19]
Example 1 Example 2 Example 3
Conditional expression (1) ΔPgFp1 0.009 0.012 0.012
Conditional expression (2) NdL1n 1.904 1.954 1.904
Conditional expression (3) β2w -0.213 -0.201 -0.220
Conditional expression (4) |ΔA|/RP 0.009 0.029 0.009
Conditional expression (5) f2/frn 0.358 0.448 0.413
Conditional expression (6) CrL1f/fw 6.292 8.284 5.668
Conditional expression (7) β2t -0.572 -0.837 -0.661
Conditional expression (8) NdLnr 1.904 1.923 1.904
Conditional expression (9) |X1|/ft 0.551 0.348 0.563
Conditional expression (10) D2rt/ft 0.036 0.017 0.036
Conditional expression (11) βrw -0.927 -0.913 -0.980
Conditional expression (12) |(1−βvct)×βvctr| 1.512 1.890 1.527
Conditional expression (13) f1/ft 0.902 0.518 0.826
Conditional expression (14) f2/fw -0.807 -0.832 -0.762
Conditional expression (15) D2rw/fw 1.137 1.548 1.148

[Table 20]
Example 1 Example 2 Example 3
ΔA -0.078 -0.204 -0.068
RP 8.752 6.980 7.929
f2 -14.876 -15.380 -14.105
frn -41.535 -34.316 -34.131
CrL1f 116.044 153.209 104.897
FW 18.442 18.495 18.508
X1 -57.031 -67.587 -58.676
ft 103.541 194.355 104.128
D2rt 3.740 3.352 3.721
βvct 0.358 -0.488 0.289
βvctr −2.356 −1.271 −2.146
f1 93.429 100.685 85.996
D2rw 20.976 28.631 21.252

According to the present invention, it is possible to provide a compact zoom lens and an imaging device with high optical performance while reducing costs.

G1...first lens group G2...second lens group G3...third lens group G4...fourth lens group G5...fifth lens group G6...sixth lens group G7 ... Seventh lens group S ... Aperture diaphragm CG ... Cover glass IMG ... Image plane

Claims (14)

Consists of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear group consisting of three or more lens groups having positive refractive power as a whole. is,
A zoom lens that performs zooming by changing the distance between adjacent lens groups,
The first lens group includes a lens L1n having negative refractive power disposed closest to the object side and a lens having positive refractive power, and the lens L1n is the lens having positive refractive power. spliced,
Abbe numbers in the d-line of the lenses having positive refractive power included in the first lens group are all 48 or more,
the second lens group does not include an aspherical surface;
The rear group has at least one lens with negative refractive power,
the rear group includes at least one lens surface rn having a concave shape on the image side;
A zoom lens that satisfies the following conditional expression.
1.85 < NdL1n < 2.20 (2)
1.86<NdLnr<2.20 (8)
-0.90 < β2t < -0.45 (7)
0.20<f2/frn< 0.55 (5-1)
5.50<CrL1f/fw<1000.00 (6-1)
−0.832≦f2/fw<−0.50 (14)
however,
NdL1n: Refractive index at the d-line of the lens L1n having negative refractive power NdLnr: Refractive index at the d-line of the lens Lnr with the highest refractive index among the lenses having negative refractive power included in the rear group β2t: lateral magnification of the second lens group at the telephoto end f2: focal length of the second lens group frn: focal point of the lens surface having the largest absolute value of negative refractive power among the lens surfaces rn included in the rear group Distance CrL1f: Radius of curvature of the lens surface closest to the object side of the first lens group fw: Focal length of the zoom lens at the wide-angle end Consists of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a rear group consisting of three or more lens groups having positive refractive power as a whole. is,
A zoom lens that performs zooming by changing the distance between adjacent lens groups,
The first lens group is composed of a lens L1n having negative refractive power disposed closest to the object side, and two lenses having positive refractive power, and the lens L1n comprises the two positive refractive power lenses. cemented with one of the lenses having power,
Abbe numbers at the d-line of the lenses having positive refractive power included in the first lens group are all 51 or more,
The rear group has at least one lens with negative refractive power,
the rear group includes at least one lens surface rn having a concave shape on the image side;
A zoom lens that satisfies the following conditional expression.
1.85 < NdL1n < 2.20 (2)
1.86<NdLnr<2.20 (8)
-0.90 < β2t < -0.45 (7)
0.20<f2/frn<0.80 (5)
5.50<CrL1f/fw<1000.00 (6-1)
-1.10 < βrw < -0.65 (11-1)
−0.832≦f2/fw<−0.50 (14)
however,
NdL1n: Refractive index for the d-line of the lens L1n having negative refractive power NdLnr: Refractive index for the d-line of the lens Lnr with the highest refractive index among the lenses having negative refractive power included in the rear group β2t: Lateral magnification of the second lens group at the telephoto end f2: focal length of the second lens group frn: focal point of the lens surface having the largest negative refractive power among the lens surfaces rn included in the rear group distance
CrL1f: radius of curvature of the lens surface closest to the object side in the first lens group
βrw: Combined lateral magnification of the rear group at the wide-angle end fw: Focal length of the zoom lens at the wide-angle end the rear group has an aspherical surface ra convex to the object side;
3. The zoom lens according to claim 1, wherein the aspherical surface ra has a shape in which the refractive power in the peripheral portion is weaker than the refractive power in the paraxial spherical surface defined by the paraxial radius of curvature. 4. The zoom lens according to claim 3, which satisfies the following conditional expression.
0.002<|ΔA|/RP<0.080 (4)
however,
RP: Maximum effective radius of the aspheric surface ra included in the rear group ΔA: Defined by the sag amount of the aspheric surface ra at the height position of RP from the optical axis and the paraxial radius of curvature of the aspheric surface ra Difference from paraxial sphere sag amount 5. The zoom lens according to any one of claims 1 to 4, which satisfies the following conditional expression.
0.0000<ΔPgFp1<0.0180 (1)
however,
ΔPgFp1: the anomalous dispersion of the lens having the largest anomalous dispersion among the lenses having positive refractive power included in the first lens group, where the anomalous dispersion is the partial dispersion ratio on the vertical axis and the d-line In the coordinate system with the Abbe number νd as the horizontal axis, the coordinates of the glass material C7 with a partial dispersion ratio of 0.5393 and νd of 60.49 and the coordinates of the glass material F2 with a partial dispersion ratio of 0.5829 and νd of 36.30. The deviation from the reference line of the partial dispersion ratio when the straight line passing through 6. The zoom lens according to any one of claims 1 to 5, which satisfies the following conditional expression.
-0.35 < β2w < -0.12 (3)
however,
β2w: lateral magnification at the wide-angle end of the second lens group The zoom lens according to any one of claims 1 to 6 , wherein the first lens group moves along the optical axis when zooming from the wide-angle end to the telephoto end. 8. A zoom lens according to claim 7, which satisfies the following conditional expression.
0.01<|X1|/ft<0.70 (9)
however,
X1: Distance from the position closest to the image side to the position closest to the object side where the first lens group is positioned during zooming from the wide-angle end to the telephoto end ft: the focal length of the zoom lens at the telephoto end 9. The zoom lens according to any one of claims 1 to 8, which satisfies the following conditional expression.
0.010<D2rt/ft<0.040 (10)
however,
D2rt: distance on the optical axis between the most image-side lens surface of the second lens group and the most object-side lens surface of the rear group at the telephoto end ft: the focal length of the zoom lens at the telephoto end 2. A zoom lens according to claim 1, which satisfies the following conditional expression.
−1.50 < βrw < −0.65 (11)
however,
βrw: Combined lateral magnification of the rear group at the wide-angle end 11. The rear group according to any one of claims 1 to 10 , wherein the rear group includes an anti-vibration group capable of shifting an image by moving in a direction substantially perpendicular to the optical axis, and satisfying the following conditional expression: The zoom lens described in .
0.50<|(1−βvct)×βvctr|<6.00 (12)
however,
βvct: Lateral magnification of the anti-vibration group at the telephoto end when focused on infinity βvctr: Composite lateral magnification of all lenses arranged closer to the image side than the anti-vibration group on the telephoto end when focused on infinity 12. The zoom lens according to any one of claims 1 to 11, which satisfies the following conditional expression.
0.40<f1/ft<1.20 (13)
however,
f1: focal length of the first lens group ft: focal length of the zoom lens at the telephoto end 13. The zoom lens according to any one of claims 1 to 12, which satisfies the following conditional expression.
0.80<D2rw/fw<2.00 (15)
however,
D2rw: Distance on the optical axis between the most image-side lens surface of the second lens group and the most object-side lens surface of the rear group at the wide-angle end 14. A zoom lens according to any one of claims 1 to 13 , and an imaging device provided on the image side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal. An imaging device characterized by:

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