JP2006030582A - Large-diameter zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens comprising four groups of, in order from the object side, positive, negative, negative, and positive powers and using the second and third ones of them as groups moved for zooming, the zoom lens being designed such that the thickness of the fourth group is made compact and a movement space for the groups moved for zooming is ensured, thereby satisfactory optical performance having a zoom ratio of about 7.7 is realized with the large-diameter zoom lens whose F-number is approximately 1.2 and view angle is approximately 54°, and miniaturization is also accomplished. <P>SOLUTION: The large-diameter zoom lens comprises in order from the object side: the first lens group G<SB>1</SB>of positive power fixed for variable magnification; second lens group G<SB>2</SB>of negative power and third lens group G<SB>3</SB>of negative power which are groups moved for zooming; and fourth lens group G<SB>4</SB>of positive power fixed for variable magnification. The fourth lens group G<SB>4</SB>includes a diaphragm 1, and a ninth lens L<SB>9</SB>right behind the diaphragm 1 is a double-sided aspheric lens. The thickness of the fourth lens group G<SB>4</SB>satisfies 3.5>D<SB>G4</SB>/f<SB>w</SB>. The second lens group G2 comprises, in order from the object side, a meniscus lens of negative power whose convex face is disposed on the object side, and a cemented lens composed of a biconcave lens and a lens of positive power whose convex face is disposed on the object side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a large-aperture zoom lens, and more particularly to a large-aperture zoom lens suitably used for a surveillance camera or the like equipped with a CCD.

  Since lenses used for surveillance cameras are often used mainly indoors, a bright large-diameter lens is required. For the purpose of monitoring, a zoom function is highly useful.

  As such a zoom lens, for example, in Patent Document 1, a positive first lens group, a negative second lens group, a negative third lens group, and a positive fourth lens group are arranged in order from the object side. A zoom lens having a configuration in which the second lens group and the third lens group move during zooming is described.

Japanese Patent No. 3088141

  However, in recent years, the zoom ratio is larger than that of the above-described conventional example even when the angle of view is as bright as that of the above-described conventional example and the angle of view at the wide-angle end is also the same. What is needed is requested.

  As a problem to satisfy this demand, it is generally possible to increase the zoom ratio by increasing the amount of movement of a lens group that moves during zooming (hereinafter sometimes referred to as a zoom movement group). However, there is a circumstance that the zoom lens size is increased only by changing it. In addition, in order to obtain a desired zoom ratio without changing the amount of movement of the zoom movement group, when the refractive power of these lens groups is increased, the optical performance is significantly deteriorated such that spherical aberration is likely to occur. Is not realistic.

  The present invention has been made in view of such circumstances. Even when the angle of view at the wide-angle end is the same as that of the conventional example, the zoom ratio is larger, and in spite of that, the zoom lens The object is to provide a large-aperture zoom lens with a smaller size.

  Specifically, in a large-aperture zoom lens having an F number of about 1.2 and an angle of view of about 54 degrees at the wide-angle end and a zoom ratio of about 7.7 times, the large-aperture zoom lens is miniaturized. For the purpose. Note that “about” is added to each numerical value of the F number, the angle of view, and the zoom ratio indicates that it includes at least a numerical range of 10%.

The large-aperture zoom lens of the present invention, in order from the object side, corrects the first lens group having a positive refractive power that is fixed during zooming, continuous zooming, and image plane movement caused by the continuous zooming, A second lens group having a negative refractive power and a third lens group having a negative refractive power that move in relation to each other, and a fourth lens group having a fixed positive refractive power at the time of zooming are arranged. And
The fourth lens group includes at least one double-sided aspheric lens, and satisfies the following conditional expression (1).

3.5> D _G4 / f _w (1)
here,
f _w : Focal length of the entire lens system at the wide angle end D _G4 : On-axis distance from the most object side surface to the most image side surface in the fourth lens group

  The fourth lens group preferably includes a stop, and the first or second lens immediately after the stop is preferably an aspheric lens.

  The second lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave lens and a positive lens having a convex surface facing the object side in order from the object side. It is preferable to be made.

  According to the large-aperture zoom lens of the present invention, in order from the object side, a fixed positive first lens group at the time of zooming, a negative second lens group and a negative third lens group as a zoom movement group, and The fourth lens group that is fixed and positive at the time of zooming is arranged, satisfies a predetermined conditional expression regarding the lens group length of the fourth lens group, and includes at least one double-sided aspheric lens in the fourth lens group A large aperture zoom with a large zoom ratio and a smaller zoom lens size without sacrificing optical performance. A lens can be obtained. Specifically, in a large aperture zoom lens having an F number of about 1.2, an angle of view at the wide angle end of about 54 degrees, and a zoom ratio of about 7.7 times, the large aperture zoom lens can be downsized. Can be planned.

  Hereinafter, embodiments of a large-aperture zoom lens according to the present invention will be described with reference to the drawings. FIG. 1 shows the lens configuration of a large-aperture zoom lens according to Example 1 of the present invention, which will be described with reference to this figure as a representative.

As shown in FIG. 1, the large-aperture zoom lens according to the present invention includes, in order from the object side, a first lens group G ₁ that has a fixed positive refractive power during zooming, continuous zooming, and continuous zooming. The second lens group G ₂ having a negative refractive power and the third lens group G ₃ having a negative refractive power that move in relation to each other are corrected, and fixed at the time of zooming. the fourth lens group G ₄ having a positive refractive power are arrayed. The fourth lens group G ₄ includes an aspherical lens in which at least one of both surfaces are aspherical. In Figure 1, the ninth lens L ₉ is a double-sided aspheric lens. In the large-aperture zoom lens of the present invention, the aspheric surface of the aspheric lens is represented by the following aspheric expression.

The large-aperture zoom lens of the present invention satisfies the following conditional expression (1).
3.5> D _G4 / f _w (1)
here,
f _w : focal length of the entire lens system at the wide-angle end D _G4 : axial distance from the most object-side surface to the most image-side surface in the fourth lens group G ₄

A large diameter zoom lens of the present invention, by the structure described above, the positive from the object side, a negative, negative, positive in 4 groups constituting the second lens group G ₂ and the third lens group G ₃ is zoom A large-aperture zoom lens configured as a moving group is as bright as a conventional large-aperture zoom lens, and even with the same angle of view at the wide-angle end, the zoom ratio is larger, and zooming is possible. The lens size can be made smaller.

  Specifically, in a large-aperture zoom lens having an F number of about 1.2 and an angle of view of about 54 degrees at the wide-angle end and a zoom ratio of about 7.7 times, the large-aperture zoom lens is miniaturized. It becomes possible. Note that “about” is added to each numerical value of the F number, the angle of view, and the zoom ratio indicates that it includes at least a numerical range of 10%.

In addition, as an index for reducing the size of the zoom lens, in the large-aperture zoom lens of the present invention, D _SUM / f _W (where D _SUM : from the most object-side surface of the first lens group G ₁ to the imaging surface 3 is used. , F _W : the focal length of the entire lens system at the wide angle end). Specifically, it is assumed that downsizing is achieved when the value is smaller than 12.2. The value of D _SUM in the present invention because it is constant regardless zoom position, by setting the upper limit value in comparison with the focal length of a short wide-angle end most focal length, it can be indicative of miniaturization. According to the large-aperture zoom lens of the present invention, it is possible to reduce the size of the zoom lens so that the value of D _SUM / f _W is also smaller than 12.2.

A large diameter zoom lens of the present invention, while allowing a sufficiently large space for moving the zooming movement group G _2, G ₃ to the large lenses of the zoom ratio as described above, with respect to the thickness of the fourth lens group G ₄ the fourth lens group G ₄ defines the upper limit of conditional expression (1) so as to constitute a compact. Thereby, even with the F number and the angle of view as described above, the optical performance is good and the zoom lens size can be reduced.

If the F-number, field angle, and zoom ratio premised on the large-aperture zoom lens according to the present invention are the same, and the lens is downsized to the same extent, the fourth lens exceeds the upper limit of conditional expression (1). If the total length of the group G ₄ is increased, it is not possible to secure a sufficient movement space for the zoom movement groups G ₂ and G _3. Nevertheless, in order to obtain a desired zoom ratio, these lens groups G ₂ , large forced the refractive power of G _3. For this reason, spherical aberration and coma increase, and correction becomes difficult.

Further, in a large-aperture zoom lens of the present invention, by the fourth lens group G ₄ including at least one bi-aspherical lens, in a large lens zoom ratio as described above, the fourth lens group G ₄ While being compact, good optical performance can be obtained.

Note that it is more preferable from the viewpoint of miniaturization of the zoom lens if the following conditional expression (1 ′) is satisfied instead of the conditional expression (1).
3.1> D _G4 / f _w (1 ')

Further, as an index relates to the thickness of the fourth lens group G ₄ described above, a large-aperture zoom lens of the present invention, D _{G4 /} IS which is the ratio of the value of D _G4 described above for the image size (although, IS: Image Size) We focus on the numerical value. _{Specifically,} the value of _D G4 / IS is _3.6> by setting such that the _D G4 / IS, as a lens practically realistic size, desired F number, angle, zoom ratio The large-diameter zoom lens can be reduced in size. Moreover, it is more preferable in terms of the above-mentioned size reduction to set so that 3.2> D _G4 / IS. In the example described later, the image size IS is assumed to be Φ8.0 mm. As its application, for example, there is a small television camera such as a surveillance camera, and the large-aperture zoom lens of the present invention is suitable for such an application.

Further, in a large-aperture zoom lens of the present invention as described above, in order to a large lens zoom ratio, while the moving space of the zoom moving group G _2, G ₃ so as to sufficiently large, the fourth lens group G ₄ It is designed to be compact. As an index related to the movement space of the zoom movement groups G ₂ and G ₃ , in the large-aperture zoom lens of the present invention, D _G2G3 / D _SUM (where D _G2G3 : first lens group G ₁₎ with the above-mentioned D _SUM as the denominator. most are from the surface of the imaging surface by focusing the numerical distance) to the most object side surface of the fourth lens group G ₄ of. In other words, D _G2G3 is a movement space of the zoom movement groups G ₂ and G ₃ .

_{Specifically,} the value of _D G2G3 _/ D _{SUM is, 0.35 <D} G2G3 _/ by setting it to such a _{D SUM,} operational effects substantially similar to the conditional expression (1), the zoom moving group _{G 2} , while allowing a sufficiently large space for moving G _3, the fourth lens group G ₄ can be made compact, the zoom ratio as described above, be of F number and field angle, the optical performance As a result, the zoom lens size can be reduced.

Further, in the large-aperture zoom lens, the fourth lens group G ₄ includes a diaphragm, it is preferable that the first sheet or the second sheet of the lens immediately after the diaphragm is formed in an aspheric lens. In FIG. 1, the ninth lens L ₉ , which includes the diaphragm 1 and is the first lens immediately after the diaphragm 1, is a double-sided aspheric lens.

In general, in order to use for imaging with a CCD, it is important that the principal ray be incident on the imaging surface so as to be substantially parallel to the optical axis. the technique of placing the imaging surface side of the most object side, or the most object side lens in the fourth lens group G ₄ of the fourth lens group G ₄ having a positive refractive power are known in fixed. Here, in the large-aperture zoom lens according to the present invention, it is preferable that the light beam passes through a relatively high position at the latter position and the angle of the principal light beam with respect to the optical axis is small, and the stop 1 is disposed at that position. .

By arranging the stop 1 in this way and arranging the aspheric lens at the subsequent stage as described above, the spherical aberration correction function of the aspheric lens can be efficiently exhibited with respect to the light flux, and as a result, the light flux It can be used without waste. Therefore, by disposing the aspherical lens at such a position, in the large-diameter zoom lens, while also constituting the fourth lens group G ₄ to the compact, it is possible to obtain good optical performance.

In order to efficiently exhibit the spherical aberration correction function of the aspherical lens with respect to the light flux, it is desirable that the aspherical lens is the first one immediately after the stop 1, but the second one immediately after the stop 1 is used. The same function and effect can be obtained with this lens. Further, in the case of the first sheet or the second sheet of the lens immediately after the stop in the fourth lens group G ₄ and aspheric lens, as shown in FIG. 1, a lens with both surfaces aspheric lens It is preferable.

Further, in the large-aperture zoom lens, the second lens group G ₂ includes, in order from the object side, a negative meniscus lens having a convex surface directed toward the object side, as well as a convex surface facing the double concave lens and the object side in order from the object side It is preferable that a cemented lens with a positive lens is arranged. In FIG. 1, the fourth lens L ₄ to the sixth lens L ₆ correspond to these.

When the attempt is made to miniaturize the large-aperture zoom lens, generally it will be configured to increase the refractive power of the positive first lens group G _1, the positive refractive power of the first lens group G ₁ If it is increased, there is a possibility that the variation of the spherical aberration is increased depending on the configuration of the second lens in the latter stage which is also the zoom movement group. By configuring the second lens group G ₂ by three described above, small effects as I effects as the cooperation with the second lens group G ₂ overall lens shape, a large-aperture zoom lens of the cemented lens Thus, it is possible to satisfactorily correct the spherical aberration while achieving the above.

  Next, three examples of the large-aperture zoom lens of the present invention will be specifically described. In the description of each embodiment, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

<Example 1>
The lens configuration at the wide-angle end and the telephoto end of the large-aperture zoom lens according to Example 1 and the movement locus of the zoom movement group are shown in FIG. As shown in FIG. 1, the large-aperture zoom lens has, in order from the object side, a first lens group G ₁ having a positive refractive power that is fixed during zooming, continuous zooming, and an image generated by the continuous zooming. The second lens group G ₂ having a negative refractive power and the third lens group G ₃ having a negative refractive power that move on the optical axis X relative to each other by correcting the surface movement, and at the time of zooming fixed in it is the fourth lens group G ₄ is arranged to have a positive refractive power, the light flux incident from the object side, is intended to efficiently focused on the image plane 3. The fourth lens group G ₄ includes a diaphragm 1, the filter 2 is disposed on the image plane side of the fourth lens group G _4.

Here, the first lens group G ₁ includes a first lens L ₁ composed of a negative meniscus lens having a convex surface facing the object side and a second lens L ₂ composed of a biconvex lens having a surface having a large curvature facing the object side. a cemented lens, and the third lens L ₃ are formed of a positive meniscus lens having a convex surface directed toward the object side, they are arranged in order from the object side.

The second lens group G ₂ includes a fourth lens L ₄ is a negative meniscus lens having a convex surface directed toward the object _side, and the object side in the fifth lens L ₅ and the object side, which is a biconcave lens having a surface with a greater curvature a cemented lens of a sixth lens L ₆ made of a biconvex lens having a surface with a greater curvature, are arranged in order from the object side.

The third lens group G ₃ is composed of a seventh lens L ₇ consisting of a negative meniscus lens having a convex surface directed toward the image plane side.

The fourth lens group G ₄ is the eighth lens L ₈ made of a biconvex lens having a large curvature surface on the object _side, a diaphragm 1, both surfaces made of a biconvex lens having a large curvature surface on the object side aspherical The ninth lens L ₉ , the tenth lens L ₁₀ consisting of a positive meniscus lens having a convex surface facing the object side, the eleventh lens L ₁₁ consisting of a biconcave lens having a surface with a large curvature facing the object side, the imaging surface side A 12th lens L ₁₂ composed of a biconvex lens having a surface with a large curvature facing the lens, a 13th lens L ₁₃ composed of a negative meniscus lens having a convex surface facing the object side, and a biconvex lens having a surface having a large curvature facing the object side. A fourteenth lens L ₁₄ and a fifteenth lens L ₁₅ composed of a biconvex lens having a surface with a large curvature facing the object side are arranged in order from the object side.

  In the upper part of Table 1, the radius of curvature R (mm) of each lens surface of the large-aperture zoom lens, the center thickness of each lens, and the air space between each lens (hereinafter collectively referred to as the shaft upper surface space) D ( mm), and the refractive index N and the Abbe number ν at the d-line of each lens. In Table 1 and Tables 3 and 5 below, the numbers in the table represent the order from the object side, and the surface marked with a ☆ on the right side of the number is an aspheric surface. The radius of curvature R of these aspheric surfaces is shown as the value of the radius of curvature R on the optical axis in each table. However, in the corresponding lens configuration diagram, the leader line is not necessarily in the optical axis. Some are not drawn from the intersection.

Also, in the lower part of Table 1, the distance D ₅ (* 1) between the first lens group G ₁ and the second lens group G _{2 at} the wide-angle end (wide) and the telephoto end (tele) in Example 1, the second lens group The distance D ₁₀ (* 2) between G ₂ and the third lens group G ₃ , the distance D ₁₂ (* 3) between the third lens group G ₃ and the fourth lens group G ₄ , and the focal length of this large-aperture zoom lens f '(mm), and Fno. Indicates the value of.

Table 2 shows the values of the constants K, A ₄ , A ₆ , A ₈ , and A ₁₀ of the aspheric formula for the aspheric surfaces.

<Example 2>
FIG. 2 shows the lens configuration of the large-aperture zoom lens according to Example 2 at the wide-angle end and the telephoto end, and the movement locus of the zoom movement group. The large-aperture zoom lens, as shown in FIG. 2, although there is a one and substantially the same configuration in Example 1, except that the sixth lens L ₆ is a positive meniscus lens having a convex surface directed toward the object side, and configuration of the fourth lens group G ₄ is different.

The fourth lens group G ₄ is the eighth lens L ₈ made of a biconvex lens having a large curvature surface on the object _side, aperture stop 1, both surfaces consist meniscus lens of double-sided same curvature having a convex surface facing the object side is aspherical A ninth lens L ₉ , a tenth lens L ₁₀ composed of a biconvex lens having a surface with a large curvature facing the object side, an eleventh lens L ₁₁ composed of a negative meniscus lens having a convex surface facing the image forming surface, A twelfth lens L ₁₂ composed of a biconvex lens having a surface with a large curvature facing the image surface side, a thirteenth lens L ₁₃ composed of a negative meniscus lens with a convex surface facing the object side, and a surface with a large curvature facing the imaging surface side In addition, a fourteenth lens L _{14 made of} a biconvex lens and a fifteenth lens L ₁₅ made of a biconvex lens having a surface with a large curvature facing the object side are arranged in this order from the object side.

In the upper part of Table 3, the radius of curvature R (mm) of each lens surface of this large-aperture zoom lens, the axial top surface distance D (mm) of each lens, the refractive index N and the Abbe number ν in the d-line of each lens Indicates. In the lower part of Table 3, the distance D ₅ (* 1) between the first lens group G ₁ and the second lens group G _{2 at} the wide-angle end (wide) and the telephoto end (tele) in Example 2 and the second lens group The distance D ₁₀ (* 2) between G ₂ and the third lens group G ₃ , the distance D ₁₂ (* 3) between the third lens group G ₃ and the fourth lens group G ₄ , and the focal length of this large-aperture zoom lens f '(mm), and Fno. Indicates the value of.

Table 4 shows the values of the constants K, A ₄ , A ₆ , A ₈ , and A ₁₀ of the aspheric formula for the aspheric surfaces.

<Example 3>
FIG. 3 shows the lens configuration at the wide-angle end and the telephoto end and the movement locus of the zoom movement group of the large-aperture zoom lens according to Example 3. The large-aperture zoom lens, as shown in FIG. 3, but there is a one and substantially the same configuration in Example 1, except that the sixth lens L ₆ is a positive meniscus lens having a convex surface directed toward the object side, and configuration of the fourth lens group G ₄ is different. That is, in this embodiment, the fourth lens group G ₄ includes one set of cemented lenses as compared to the first embodiment, and the fourth lens group G ₄ is 1 in comparison with the first embodiment. It is made up of fewer sheets.

The fourth lens group G ₄ is the eighth lens L ₈ made of a biconvex lens having a large curvature surface on the object _side, aperture stop 1, both surfaces consist meniscus lens of double-sided same curvature having a convex surface facing the object side is aspherical A ninth lens L ₉ , a tenth lens L ₁₀ composed of a biconvex lens having a surface with a large curvature directed toward the object side, and an eleventh lens L ₁₁ composed of a negative meniscus lens having a convex surface directed toward the image plane. A cemented lens, a twelfth lens L ₁₂ composed of a biconvex lens having a surface with a large curvature facing the imaging surface side, a thirteenth lens L ₁₃ composed of a negative meniscus lens with a convex surface facing the object side, and a curvature toward the imaging surface side fourteenth lens L ₁₄ made of a biconvex lens having a surface with a greater, are arranged in order from the object side.

In the upper part of Table 5, the radius of curvature R (mm) of each lens surface of this large-aperture zoom lens, the axial top surface distance D (mm) of each lens, the refractive index N and the Abbe number ν in each lens d-line Indicates. In the lower part of Table 5, the distance D ₅ (* 1) between the first lens group G ₁ and the second lens group G _{2 at} the wide-angle end (wide) and the telephoto end (tele) in Example 3 and the second lens group The distance D ₁₀ (* 2) between G ₂ and the third lens group G ₃ , the distance D ₁₂ (* 3) between the third lens group G ₃ and the fourth lens group G ₄ , and the focal length of this large-aperture zoom lens f '(mm), and Fno. Indicates the value of.

Table 6 shows the values of the constants K, A ₄ , A ₆ , A ₈ , and A ₁₀ of the aspheric formula for the aspheric surfaces.

Further, in Table 7, the large-aperture zoom lenses according to Examples 1-3 above, the values corresponding to _D G4 / _{f w} of the condition (1) described above, and the above-mentioned _D SUM / _{f W,} image size IS Indicates values corresponding to D _G4 / IS and D _G2G3 / D _SUM when _{Φ8.0 mm} . In each example, the conditional expression (1) is satisfied, and the values corresponding to D _SUM / f _W , D _G4 / IS, and D _G2G3 / D _SUM are also in a desirable range. That is, these large-aperture zoom lenses have a predetermined zoom ratio, F number, and angle of view, but have a small zoom lens size.

  4 to 12 are aberration diagrams illustrating various aberrations of the large-aperture zoom lens according to Examples 1 to 3 described above. 4, 7, and 10 are aberration diagrams showing spherical aberration, astigmatism, and distortion at the wide-angle end and the telephoto end of the large-aperture zoom lenses according to Examples 1 to 3 described above. Each astigmatism diagram shows aberrations with respect to the sagittal image surface and the tangential image surface. 5, 8, and 11 are aberration diagrams showing coma aberration at the wide-angle end of the large-aperture zoom lens according to Examples 1-3, and FIGS. 6, 9, and 12 are large-diameters according to Examples 1-3. It is an aberration diagram showing coma aberration at the telephoto end of the zoom lens.

  As is apparent from FIGS. 4 to 12, according to the large-aperture zoom lenses according to Examples 1 to 3, the F number is about 1.2, the angle of view at the wide-angle end is about 54 degrees, and zooming is performed. In a large-aperture zoom lens having a ratio of about 7.7 times, good aberration correction is performed over the entire zoom area.

  The large-aperture zoom lens according to the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the number and shape of lenses constituting each lens group can be appropriately selected.

  The large-aperture zoom lens of the present invention is suitable for a small television camera such as a surveillance camera, but the application is not limited thereto, and for example, it may be used as an imaging lens for another camera. Of course it is possible.

The figure showing the structure of the large aperture zoom lens which concerns on Example 1 of this invention. The figure showing the structure of the large aperture zoom lens which concerns on Example 2 of this invention. The figure showing the structure of the large aperture zoom lens which concerns on Example 3 of this invention. Aberration diagram showing various aberrations of the large-aperture zoom lens of Example 1 Aberration diagram showing coma aberration at the wide-angle end of the large-aperture zoom lens of Example 1 Aberration diagram showing coma aberration at the telephoto end of the large-aperture zoom lens of Example 1 Aberration diagram showing various aberrations of the large-aperture zoom lens of Example 2 Aberration diagram showing coma aberration at the wide-angle end of the large-aperture zoom lens of Example 2 Aberration diagram showing coma aberration at the telephoto end of the large-aperture zoom lens of Example 2 Aberration diagram showing various aberrations of the large-aperture zoom lens of Example 3 Aberration diagram showing coma aberration at the wide-angle end of the large-aperture zoom lens of Example 3 Aberration diagram showing coma aberration at the telephoto end of the large-aperture zoom lens of Example 3

Explanation of symbols

1 stop 2 filter 3 the image plane G ₁ ~G ₄ lens group L ₁ ~L ₁₅ lens X optical axis

Claims (3)

In order from the object side, the first lens unit having a positive refracting power that is fixed during zooming, the continuous zooming, and the correction of the image plane movement caused by the continuous zooming, and the negative refraction that moves in relation to each other. A second lens group having a power, a third lens group having a negative refractive power, and a fourth lens group having a fixed positive refractive power at the time of zooming,
The fourth lens group includes at least one double-sided aspheric lens, and satisfies the following conditional expression (1).
3.5> D _G4 / f _w (1)
here,
f _w : Focal length of the entire lens system at the wide angle end D _G4 : On-axis distance from the most object side surface to the most image side surface in the fourth lens group   The large-aperture zoom lens according to claim 1, wherein the fourth lens group includes a stop, and the first lens or the second lens immediately after the stop is an aspherical lens.   The second lens group includes, in order from the object side, a negative meniscus lens having a convex surface facing the object side, and a cemented lens of a biconcave lens and a positive lens having a convex surface facing the object side in order from the object side. The large-aperture zoom lens according to claim 1 or 2, wherein:

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