JP2010117676A - Zoom lens, optical apparatus, and method for manufacturing the zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens that is compact and has high optical performance while having a relatively high variable power ratio. <P>SOLUTION: The zoom lens ZL has a first lens group G1 of negative refractive power, a second lens group G2 of positive refractive power, and a third lens group G3 of positive refractive power. If the focal distance of the zoom lens ZL at the telephoto end is denoted as ft, the focal distance of it at the wide-angle end is denoted as fw; the interval between the first and second lens groups G1 and G2 at the telephoto end is Dt12 and the interval between the first and second lens groups G1 and G2 at the wide-angle end is Dw12, the conditional expression: 0.15<(ft×Dt12)/(fw×Dw12)<0.3 is satisfied. If the radius of curvature of the object-side lens face of the first positive lens L21 is R31 and the curvature radius of the object-side lens face of the second positive lens L22 of the second lens group G2 is R41, conditional expression by 0.5<¾R31/R41¾<2.0 is satisfied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a zoom lens, an optical apparatus, and a zoom lens manufacturing method.

In recent years, there has been a strong demand for high performance and compactness in imaging devices such as video cameras and digital still cameras. In these imaging apparatuses, zoom lenses are used as photographing lenses. For example, a three-group configuration in which zooming is performed by changing the distance between lens groups by moving each lens group along the optical axis. Zoom lenses are well known. Conventionally, in such a negative / positive / positive three-group zoom lens (see, for example, Patent Document 1), various techniques have been proposed that satisfy the above requirements by making full use of aspherical lenses, cemented lenses, and the like. It was.
JP 2006-227197 A

  However, these conventional zoom lenses have a problem that the zoom ratio cannot be increased while maintaining excellent optical performance.

  The present invention has been made in view of such problems, and provides a zoom lens, an optical apparatus, and a method of manufacturing a zoom lens that have a compact and high optical performance while having a relatively high zoom ratio. With the goal.

In order to achieve such an object, the zoom lens according to the present invention includes a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side along the optical axis. And a third lens group having a positive refractive power, the first lens group includes one negative lens and one positive lens arranged in order from the object side along the optical axis. The second lens group is composed of a first positive lens, a second positive lens, a negative lens, and a third positive lens arranged in order from the object side along the optical axis. The third lens group is composed of one positive lens, the focal length of the zoom lens in the telephoto end state is ft, the focal length of the zoom lens in the wide-angle end state is fw, and the first lens in the telephoto end state is On the optical axis between the lens group and the second lens group Is Dt12, and the distance on the optical axis between the first lens group and the second lens group in the wide-angle end state is Dw12, the following expression 0.15 <(ft × Dt12) / (fw × Dw12) < 0.30
When the radius of curvature of the object-side lens surface of the first positive lens is R31 and the radius of curvature of the object-side lens surface of the second positive lens is R41, the following formula 0.5 <| R31 / R41 | <2.0
To meet the requirements of

In the zoom lens described above, when the thickness on the optical axis of the second lens group is D2 and the focal length of the second lens group is f2, the following formula 0.4 <D2 / f2 <0. 6
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the focal length of the negative lens of the first lens group is f11, the following expression 1.80 <f1 / f11 <1.95 is satisfied.
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the total length of the zoom lens in the wide-angle end state is TLw and the focal length in the wide-angle end state of the zoom lens is fw, the following formula 2.5 <TLw / (fw × ft) ^1/2 <3.0
It is preferable to satisfy the following conditions.

  In the zoom lens described above, it is preferable that the third positive lens in the second lens group has an aspherical surface.

In the zoom lens described above, when the focal length of the positive lens of the first lens group is f12 and the focal length of the zoom lens at the wide-angle end state is fw, the following expression 2.8 <f12 / fw < 3.3
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the focal length of the second lens group is f2, the following expression 0.3 <f2 / ft <0.4
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the focal length of the third lens group is f3, the following expression 0.9 <f3 / ft <1.1
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the thickness of the first lens unit on the optical axis is D1, the following expression 0.10 <D1 / (− f1) <0.35
It is preferable to satisfy the following conditions.

In the zoom lens described above, the thickness on the optical axis of the first lens group is D1, the thickness on the optical axis of the second lens group is D2, and the optical axis of the third lens group is on the optical axis. When the thickness is D3, the following formula 0.40 <(D1 + D2 + D3) / ft <0.43
It is preferable to satisfy the following conditions.

  In the zoom lens described above, the first lens group includes one negative meniscus lens having a convex surface facing the object side and a convex surface facing the object side, which are arranged in order from the object side along the optical axis. Preferably, it consists of a single positive meniscus lens.

  In the zoom lens described above, when zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, and the second lens group and the third lens It is preferred that the spacing with the group increases.

  The optical apparatus according to the present invention is an optical apparatus including a zoom lens that forms an image of an object on a predetermined surface, wherein the zoom lens is the zoom lens according to the present invention.

The zoom lens manufacturing method according to the present invention includes, in order from the object side along the optical axis, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a positive refraction. In the method for manufacturing a zoom lens in which the third lens group having power is arranged, one negative lens and one positive lens are arranged in order from the object side along the optical axis, and the first lens is arranged. A first positive lens, a second positive lens, a negative lens, and a third positive lens in order from the object side along the optical axis. The third lens group is configured by arranging one positive lens, the focal length in the telephoto end state of the zoom lens is ft, the focal length in the wide-angle end state of the zoom lens is fw, and telephoto Optical axes of the first lens group and the second lens group in the end state Is Dt12, and the distance on the optical axis between the first lens group and the second lens group in the wide-angle end state is Dw12, 0.15 <(ft × Dt12) / (fw × Dw12) ) <0.30
When the radius of curvature of the object-side lens surface of the first positive lens is R31 and the radius of curvature of the object-side lens surface of the second positive lens is R41, the following formula 0.5 <| R31 / R41 | <2.0
To meet the requirements of

  According to the present invention, it is possible to obtain a compact and high optical performance while having a relatively high zoom ratio.

  Hereinafter, preferred embodiments of the present application will be described with reference to the drawings. A digital still camera CAM provided with a zoom lens according to the present application is shown in FIG. 7A is a front view of the digital still camera CAM, FIG. 7B is a rear view of the digital still camera CAM, and FIG. 7C is taken along the arrow AA ′ in FIG. 7A. Cross-sectional views are shown respectively.

    In the digital still camera CAM shown in FIG. 7, when a power button (not shown) is pressed, a shutter (not shown) of the photographing lens (ZL) is opened, and light from the subject (object) is condensed by the photographing lens (ZL). Then, an image is formed on an image sensor C (for example, a CCD or a CMOS) disposed on the image plane I. The subject image formed on the image sensor C is displayed on the liquid crystal monitor M disposed behind the digital still camera CAM. The photographer determines the composition of the subject image while looking at the liquid crystal monitor M, and then depresses the release button B1 to photograph the subject image with the image sensor C, and records and saves it in a memory (not shown).

  The taking lens is composed of a zoom lens ZL according to an embodiment described later. Also, in the digital still camera CAM, the auxiliary light emitting unit D that emits auxiliary light when the subject is dark and the photographing lens (zoom lens ZL) are zoomed from the wide-angle end state (W) to the telephoto end state (T). Wide (W) -Tele (T) button B2 and function button B3 used for setting various conditions of the digital still camera CAM are arranged.

  The zoom lens ZL includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, an aperture S, and a positive refraction, which are arranged in order from the object side along the optical axis. And a third lens group G3 having power. Further, during zooming from the wide-angle end state to the telephoto end state, the first to third lens groups G1 to G3 move along the optical axis, respectively (for example, see FIG. 1). The distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. A filter group FL including a low-pass filter and an infrared cut filter is disposed between the zoom lens ZL and the image plane I.

  The first lens group G1 includes one negative lens and one positive lens arranged in order from the object side along the optical axis. The second lens group G2 includes a first positive lens, a second positive lens, a negative lens, and a third positive lens that are arranged in order from the object side along the optical axis. The third lens group G3 is composed of one positive lens.

  In the zoom lens ZL having such a configuration, the focal length in the telephoto end state of the zoom lens ZL is ft, the focal length in the wide-angle end state of the zoom lens ZL is fw, and the first lens group G1 and the second lens group G1 in the telephoto end state are The distance on the optical axis from the lens group G2 is Dt12, the distance on the optical axis between the first lens group G1 and the second lens group G2 in the wide-angle end state is Dw12, and the first positive of the second lens group G2 When the radius of curvature of the object-side lens surface of the lens is R31 and the radius of curvature of the object-side lens surface of the second positive lens is R41, the conditions represented by the following conditional expressions (1) and (2) Is preferably satisfied. In this way, the overall optical length can be reduced, and each aberration can be corrected well. Therefore, the zoom lens ZL having a zoom ratio of about 5 times and a compact and high optical performance can be obtained. It becomes possible to obtain an optical apparatus (digital still camera CAM) provided with this.

0.15 <(ft × Dt12) / (fw × Dw12) <0.30 (1)
0.5 <| R31 / R41 | <2.0 (2)

  Here, the conditional expression (1) defines the distance between the first lens group G1 and the second lens group G2 in the telephoto end state and the wide-angle end state. If the condition exceeds the upper limit value of conditional expression (1), the distance between the first lens group G1 and the second lens group G2 in the wide-angle end state becomes too short, and it is difficult to correct distortion and coma. Become. On the other hand, when the condition is less than the lower limit value of the conditional expression (1), the distance between the first lens group G1 and the second lens group G2 in the wide-angle end state becomes too long, and distortion and coma are corrected. It becomes difficult.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (1) to 0.20 or the upper limit value of conditional expression (1) to 0.29. Furthermore, by setting the lower limit of conditional expression (1) to 0.25, the effect of the present application can be maximized.

  Conditional expression (2) defines the relationship of the radius of curvature of the positive lens in the second lens group G2. If the condition exceeds the upper limit value of the conditional expression (2), R31 becomes larger than R41, so that the power of the first positive lens in the second lens group G2 becomes too weak, and correction of spherical aberration is performed. It becomes difficult. On the other hand, when the condition is less than the lower limit value of the conditional expression (2), R31 is smaller than R41, so that the power of the first positive lens becomes too strong, and it becomes difficult to correct spherical aberration.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (2) to 0.8 or setting the upper limit value of conditional expression (2) to 1.8. Furthermore, by setting the lower limit value of conditional expression (2) to 1.0 or the upper limit value of conditional expression (2) to 1.6, the effects of the present application can be maximized.

  In such a zoom lens ZL, when the thickness of the second lens group G2 on the optical axis is D2, and the focal length of the second lens group G2 is f2, the following conditional expression (3) is satisfied. It is preferable to satisfy the following conditions.

  0.4 <D2 / f2 <0.6 (3)

  Conditional expression (3) defines the thickness of the second lens group G2 on the optical axis. When the condition exceeds the upper limit value of conditional expression (3), it is difficult to correct coma near the paraxial axis. On the other hand, when the condition is lower than the lower limit value of the conditional expression (3), it is difficult to correct spherical aberration and off-axis aberrations.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (3) to 0.45 or the upper limit value of conditional expression (3) to 0.58. Furthermore, by setting the lower limit value of conditional expression (3) to 0.50 or the upper limit value of conditional expression (3) to 0.55, the effect of the present application can be maximized.

  In such a zoom lens ZL, it is preferable that the condition expressed by the following conditional expression (4) is satisfied, where f11 is the focal length of the negative lens of the first lens group G1.

  1.80 <f1 / f11 <1.95 (4)

  Conditional expression (4) defines the relationship between the focal length of the first lens group G1 and the negative lens of the first lens group G1. When the condition exceeds the upper limit value of the conditional expression (4), the power of the negative lens becomes too strong, and it becomes difficult to correct off-axis aberrations such as astigmatism, distortion, and lateral chromatic aberration. On the other hand, when the condition is lower than the lower limit value of the conditional expression (4), the power of the negative lens becomes too weak, and it is difficult to correct off-axis aberrations.

  In addition, the effect of this application can be exhibited more favorably by setting the upper limit of conditional expression (4) to 1.93.

  In such a zoom lens ZL, when the total length of the zoom lens ZL in the wide-angle end state is TLw and the focal length in the wide-angle end state of the zoom lens ZL is fw, the following conditional expression (5) is expressed. It is preferable to satisfy the conditions.

2.5 <TLw / (fw × ft) ^1/2 <3.0 (5)

  Conditional expression (5) defines the total length of the zoom lens ZL in the wide-angle end state. When the condition exceeds the upper limit value of conditional expression (5), it becomes difficult to correct distortion in the wide-angle end state. In addition, since the entire length of the zoom lens ZL becomes too long, the thickness of the zoom lens ZL becomes large, and compactness cannot be achieved. On the other hand, when the condition is lower than the lower limit value of the conditional expression (5), the entire length of the zoom lens ZL becomes too short, and it becomes difficult to correct aberrations in the entire zoom range.

  By setting the lower limit value of conditional expression (5) to 2.80, or the upper limit value of conditional expression (5) to 2.95, the effects of the present application can be exhibited better. Furthermore, by setting the lower limit of conditional expression (5) to 2.90, the effects of the present application can be maximized.

  In such a zoom lens ZL, it is preferable that the third positive lens of the second lens group G2 has an aspherical surface. By using an aspherical surface for such a positive lens, it becomes easy to correct spherical aberration and coma.

  In such a zoom lens ZL, when the focal length of the positive lens of the first lens group G1 is f12 and the focal length of the zoom lens ZL in the wide-angle end state is fw, the following conditional expression (6) is satisfied. It is preferable to satisfy the following conditions.

  2.8 <f12 / fw <3.3 (6)

  Conditional expression (6) defines the relationship between the positive lens of the first lens group G1 and the focal length of the entire zoom lens system in the wide-angle end state. When the condition exceeds the upper limit value of conditional expression (6), the power of the positive lens becomes too weak, and it becomes difficult to correct off-axis aberrations such as astigmatism, coma aberration, and lateral chromatic aberration. On the other hand, when the condition is less than the lower limit value of conditional expression (6), the power of the positive lens becomes too strong, and it is difficult to correct off-axis aberrations such as astigmatism, coma aberration, and lateral chromatic aberration.

  In such a zoom lens ZL, it is preferable that the condition expressed by the following conditional expression (7) is satisfied when the focal length of the second lens group G2 is f2.

  0.3 <f2 / ft <0.4 (7)

  Conditional expression (7) defines the relationship between the focal length of the second lens group G2 and the focal length of the entire zoom lens system in the telephoto end state. When the condition exceeds the upper limit value of the conditional expression (7), the power of the second lens group G2 becomes too weak, so that the lens movement amount at the time of zooming increases and the optical total length becomes long. It becomes difficult to correct astigmatism and coma in the telephoto end state. On the other hand, when the condition is less than the lower limit value of the conditional expression (7), the lens movement amount at the time of zooming is reduced and the optical total length is shortened, but it is difficult to correct spherical aberration and the like in the entire zoom range.

  In addition, the effect of this application can be exhibited more satisfactorily by setting the lower limit of conditional expression (7) to 0.34. Furthermore, by setting the lower limit of conditional expression (7) to 0.38, the effects of the present application can be exhibited to the maximum.

  In such a zoom lens ZL, it is preferable that the condition represented by the following conditional expression (8) is satisfied when the focal length of the third lens group G3 is f3.

  0.9 <f3 / ft <1.1 (8)

  Conditional expression (8) defines the relationship between the focal length of the third lens group G3 and the focal length of the entire zoom lens system in the telephoto end state. If the condition exceeds the upper limit value of the conditional expression (8), the power of the third lens group G3 becomes too weak, and it is difficult to correct astigmatism and coma in the wide-angle end state. On the other hand, when the condition is lower than the lower limit value of the conditional expression (8), the power of the third lens group G3 becomes too strong, so that it is difficult to correct astigmatism and curvature of field.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (8) to 0.95 or the upper limit value of conditional expression (8) to 1.05. Furthermore, by setting the upper limit of conditional expression (8) to 1.00, the effect of the present application can be maximized.

  In such a zoom lens ZL, it is preferable that the condition represented by the following conditional expression (9) is satisfied, where D1 is the thickness of the first lens group G1 on the optical axis.

  0.10 <D1 / (− f1) <0.35 (9)

  Conditional expression (9) defines the relationship between the thickness of the first lens group G1 and the focal length of the first lens group G1. When the condition exceeds the upper limit value of conditional expression (9), the first lens group G1 becomes thick and cannot be made compact when retracted, and it is difficult to correct astigmatism and distortion. On the other hand, when the condition is less than the lower limit value of the conditional expression (9), the thickness when retracted is thin, but it is difficult to correct astigmatism and distortion in the wide-angle end state.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (9) to 0.20 or the upper limit value of conditional expression (9) to 0.34. Further, by setting the lower limit value of conditional expression (9) to 0.30 or the upper limit value of conditional expression (9) to 0.32, the effect of the present application can be maximized.

  In such a zoom lens ZL, the thickness on the optical axis of the first lens group G1 is D1, the thickness on the optical axis of the second lens group G2 is D2, and the optical axis of the third lens group G3. When the upper thickness is D3, it is preferable to satisfy the condition represented by the following conditional expression (10).

  0.40 <(D1 + D2 + D3) / ft <0.43 (10)

  Conditional expression (10) defines the total thickness of each lens group. If the condition exceeds the upper limit value of conditional expression (10), the total thickness of each lens group becomes too large to be compact when retracted, and it is difficult to correct astigmatism and curvature of field. Become. On the other hand, when the condition is less than the lower limit value of the conditional expression (10), the thicknesses of the first lens group G1 and the second lens group G2 cannot be secured, and correction of field curvature and the like becomes difficult.

  In addition, the effect of this application can be exhibited more favorably by setting the upper limit of conditional expression (10) to 0.42.

  In such a zoom lens ZL, the first lens group G1 is arranged in order from the object side along the optical axis, with one negative meniscus lens having a convex surface facing the object side, and a convex surface facing the object side. Preferably, it is composed of a single positive meniscus lens. By adopting such a configuration for the first lens group G1, the outer diameter of the first lens group G1 can be reduced, and distortion, astigmatism in the wide-angle end state, and spherical aberration in the telephoto end state can be corrected well. can do.

  Further, in such a zoom lens ZL, the distance between the first lens group G1 and the second lens group G2 is reduced and the second lens group G2 and the third lens group 3 are changed during zooming from the wide-angle end state to the telephoto end state. It is preferable that the distance from the lens group G3 increases.

  Here, a method of manufacturing the zoom lens ZL having the above-described configuration will be described with reference to FIG. First, the first lens group G1, the second lens group G2, and the third lens group G3 of the present embodiment are assembled in a cylindrical barrel (step S1). When incorporating each lens into the lens barrel, the lens groups may be incorporated into the lens barrel one by one in the order along the optical axis, and a part or all of the lens groups are integrally held by the holding member, and then the lens barrel member and It may be assembled. After assembling each lens group in the lens barrel, it is confirmed whether an object image is formed in a state where each lens group is incorporated in the lens barrel, that is, whether the centers of the lens groups are aligned (step S2). ). Then, after confirming whether an image is formed, various operations of the zoom lens ZL are confirmed (step S3).

  As an example of various operations, a zooming operation in which a lens group for zooming (in the present embodiment, the first to third lens groups G1 to G3) moves along the optical axis direction, or from a long-distance object. A focusing operation in which a lens group (in this embodiment, the third lens group G3) that focuses on a distance object moves along the optical axis direction, at least some of the lenses have a component orthogonal to the optical axis. An image stabilization operation that moves like this can be cited. In the present embodiment, during zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the second lens group G2 and the third lens The interval with the group G3 is increased. In addition, the confirmation order of various operations is arbitrary. According to such a manufacturing method, it is possible to obtain a zoom lens ZL having a compact and high optical performance while having a zoom ratio of about 5 times.

(First embodiment)
Embodiments of the present application will be described below with reference to the accompanying drawings. First, a first embodiment of the present application will be described with reference to FIGS. FIG. 1 is a diagram illustrating a configuration of a zoom lens and a zoom trajectory according to the first embodiment. As described above, the zoom lens ZL according to the first example includes the first lens group G1 having a negative refractive power and the second lens having a positive refractive power arranged in order from the object side along the optical axis. The lens unit includes a group G2, a stop S, and a third lens group G3 having a positive refractive power.

  The first lens group G1 is composed of a negative meniscus lens L11 having a convex surface facing the object side and a positive meniscus lens L12 having a convex surface facing the object side, which are arranged in order from the object side along the optical axis. The lens surfaces on both sides of the lens L11 are aspheric. The second lens group G2 is arranged in order from the object side along the optical axis, a first positive meniscus lens L21 having a convex surface facing the object side, and a second positive meniscus lens L22 having a convex surface facing the object side. A negative meniscus lens L23 having a convex surface facing the object side and a third positive meniscus lens L24 having a convex surface facing the object side, and the second positive meniscus lens L22 and the negative meniscus lens L23 are cemented. Yes. The lens surfaces on both sides of the first positive meniscus lens L21 and the object-side lens surfaces of the third positive meniscus lens L24 are aspheric. The third lens group G3 includes a biconvex positive lens L31, and focusing from an infinite object to a finite distance object is performed by moving the third lens group G3 along the optical axis.

  The stop S is provided in the vicinity of the image side of the third positive meniscus lens L24, and moves together with the second lens group G2 during zooming from the wide-angle end state to the telephoto end state. It has become. The filter group FL disposed between the zoom lens ZL and the image plane I includes a low-pass filter, an infrared cut filter, and the like.

  In the zoom lens ZL having such a configuration, the first to third lens groups G1 to G3 move along the optical axis during zooming from the wide-angle end state to the telephoto end state. The distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. At this time, the first lens group G1 once moves to the image side and then moves to the object side, the second lens group G2 monotonously moves to the object side, and the third lens group G3 once moves to the object side and then the image. Move to the side.

  In the following, Tables 1 to 3 are shown, and these are tables listing the values of the specifications of the zoom lenses according to the first to third examples. In [Overall specifications] in each table, f is a focal length, FNO is an F number, ω is a half angle of view (maximum incident angle: unit is “°”), Y is an image height, and TL is a total lens length. And Bf represents the back focus. In [Lens Data], the surface number is the order of the lens surfaces counted from the object side, r is the radius of curvature of the lens surfaces, d is the distance between the lens surfaces, and nd is the d-line (wavelength λ = 587.6 nm). ), And νd represents the Abbe number for the d-line (wavelength λ = 587.6 nm). Note that * attached to the right of the surface number indicates that the lens surface is an aspherical surface. Also, the description of “1.00000” which is the refractive index of air is omitted, and the curvature radius “∞” indicates a plane.

The aspheric coefficient shown in [Aspheric data] is y along the height perpendicular to the optical axis, along the optical axis from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y. X (y), the radius of curvature of the reference sphere (paraxial radius of curvature) as R, the conic constant as κ, and the aspheric coefficient of the nth order (n = 4, 6, 8, 10) as An. Is expressed by the following conditional expression (11). In each example, the secondary aspherical coefficient A2 is 0, and the description is omitted. In [Aspherical data], “En” indicates “× 10 ⁻ⁿ ”.

X (y) = (y ² / R) / {1+ (1−κ × y ² / R ² ) ^1/2 }
^{+ A4 × y 4 + A6 ×} y 6 + A8 × y 8 + A10 × y 10 ... (11)

  In [variable interval data], d4 is the axial air interval between the first lens group G1 and the second lens group G2, and d12 is the axis between the second lens group G2 (aperture S) and the third lens group G3. The upper air interval, d14, indicates the axial air interval between the third lens group G3 and the filter group FL. These axial air intervals (d4, d12, d14) change during zooming. In addition, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or reduced. However, the same optical performance can be obtained, and the present invention is not limited to this. In addition, the same reference numerals as those in the present embodiment are used in the specification values of the second to third embodiments described later.

  Table 1 below shows specifications in the first embodiment. The surface numbers 1 to 16 in Table 1 correspond to the surfaces 1 to 16 in FIG. 1, and the group numbers G1 to G3 in Table 1 correspond to the lens groups G1 to G3 in FIG. In the first embodiment, the lens surfaces of the first surface, the second surface, the fifth surface, the sixth surface, and the tenth surface are formed in an aspherical shape.

(Table 1)
[Overall specifications]
Zoom ratio = 4.73
Wide-angle middle telephoto f = 5.94 11.00 28.11
FNO = 3.57 4.44 6.51
ω = 35.68 20.44 8.22
Y = 4.05 4.05 4.05
TL = 37.85524 33.54079 43.01623
Bf = 0.6 0.6 0.6
[Lens specifications]
Surface number r d nd νd
1 * 125.7676 0.8000 1.851350 40.10
2 * 5.8024 1.7832
3 10.0056 1.8000 1.922860 20.88
4 24.2830 (d4)
5 * 6.6200 1.6000 1.497820 82.56
6 * 55.5850 0.1000
7 4.6552 1.8000 1.755000 52.32
8 26.8874 0.5000 1.903660 31.31
9 3.6032 0.8642
10 * 10.4563 1.0000 1.693500 53.22
11 44.6624 0.3000
12 ∞ (d12) Aperture S
13 51.5223 1.5000 1.603001 65.44
14 -24.8376 (d14)
15 ∞ 1.0000 1.516330 64.14
16 ∞ (Bf)
[Aspherical data]
1st surface κ = 69.5880, A4 = 5.11330E-05, A6 = -5.70910E-07, A8 = -2.86720E-09, A10 = 4.87680E-11
2nd surface κ = 0.6420, A4 = -1.21990E-04, A6 = -3.88990E-06, A8 = 4.84840E-08, A10 = -3.82510E-09
5th surface κ = 0.2393, A4 = -1.17890E-04, A6 = 2.72900E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = -79.2481, A4 = -4.02630E-04, A6 = 4.27480E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
10th surface κ = -9.1758, A4 = 2.22990E-04, A6 = -5.80890E-05, A8 = -1.15540E-06, A10 = 0.00000E + 00
[Variable interval data]
Wide angle Medium telephoto f = 5.9438 11.0000 28.1140
d4 = 16.3168 6.8801 0.6995
d12 = 3.7369 8.7251 26.8853
d14 = 4.1541 4.2882 1.7840
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 -13.7293
G2 5 11.09162
G3 13 27.99903
[Conditional value]
Conditional expression (1) (ft × Dt12) / (fw × Dw12) = 0.2028
Conditional expression (2) | R31 / R41 | = 1.4221
Conditional expression (3) D2 / f2 = 0.5287
Conditional expression (4) f1 / f11 = 1.9156
Conditional expression (5) TLw / (fw × ft) ^1/2 = 2.9284
Conditional expression (6) f12 / fw = 2.9254
Conditional expression (7) f2 / ft = 0.3945
Conditional expression (8) f3 / ft = 0.9959
Conditional expression (9) D1 / (− f1) = 0.3193
Conditional expression (10) (D1 + D2 + D3) /ft=0.4178

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied.

  FIGS. 2A to 2C are graphs showing various aberrations of the zoom lens ZL according to the first example. That is, FIG. 2A is a diagram showing various aberrations when focusing at infinity in the wide-angle end state (f = 5.94 mm), and FIG. 2B is infinite in the intermediate focal length state (f = 11.00 mm). FIG. 2C is a diagram of various aberrations at the time of focusing on infinity in the telephoto end state (f = 28.11 mm). In each aberration diagram, FNO represents an F number, and A represents a half angle of view for each image height. In each aberration diagram, d is d-line (λ = 587.6 nm), g is g-line (λ = 435.8 nm), C is C-line (λ = 656.3 nm), and F is F-line (λ = Aberration at 486.1 nm) is shown. In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. Further, in the aberration diagrams showing the spherical aberration, the solid line shows the spherical aberration, and the broken line shows the sine condition (sine condition). The description of the aberration diagrams is the same in the other examples.

  From the respective aberration diagrams, it can be seen that in the first example, various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and the optical performance is excellent. As a result, by mounting the zoom lens ZL of the first embodiment, excellent optical performance can be ensured also in the digital still camera 1.

(Second embodiment)
Hereinafter, a second embodiment of the present application will be described with reference to FIGS. FIG. 3 is a diagram illustrating the configuration and zoom trajectory of the zoom lens according to the second example. The zoom lens of the second embodiment has the same configuration as that of the zoom lens of the first embodiment except for the position of the aspherical surface. Description is omitted. In the second example, the image-side lens surface of the negative meniscus lens L11 of the first lens group G1 is aspheric, and the lens surfaces on both sides of the first positive meniscus lens L21 are aspheric. In addition, the object-side lens surface of the third positive meniscus lens L24 is aspheric.

  Table 2 below shows specifications in the second embodiment. The surface numbers 1 to 16 in Table 2 correspond to the surfaces 1 to 16 in FIG. 3, and the group numbers G1 to G3 in Table 2 correspond to the lens groups G1 to G3 in FIG. In the second example, the lens surfaces of the second surface, the fifth surface, the sixth surface, and the tenth surface are formed in an aspherical shape.

(Table 2)
[Overall specifications]
Zoom ratio = 4.73
Wide-angle middle telephoto f = 5.94 11.00 28.11
FNO = 3.57 4.44 6.58
ω = 35.93 20.44 8.25
Y = 4.05 4.05 4.05
TL = 37.83231 33.518 42.98404
Bf = 0.6 0.6 0.6
[Lens specifications]
Surface number r d nd νd
1 160.0467 0.8000 1.851350 40.10
2 * 5.9439 1.7832
3 10.2944 1.6000 1.922860 20.88
4 25.0000 (d4)
5 * 6.6029 1.6000 1.497820 82.56
6 * 3570.7611 0.1000
7 4.7330 1.8000 1.755000 52.32
8 19.5534 0.5000 1.903660 31.31
9 3.5240 0.8642
10 * 13.9368 1.0000 1.693500 53.22
11 99.9994 0.2000
12 ∞ (d12) Aperture S
13 51.5223 1.5000 1.603001 65.44
14 -24.8376 (d14)
15 ∞ 1.0000 1.516330 64.14
16 ∞ (Bf)
[Aspherical data]
2nd surface κ = 0.6590, A4 = -1.75830E-04, A6 = -7.07630E-06, A8 = 1.72870E-07, A10 = -4.52220E-09
5th surface κ = 0.3442, A4 = -1.75940E-04, A6 = -5.26430E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = 8.0000, A4 = -3.51860E-04, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
10th surface κ = -2.5603, A4 = -3.83090E-04, A6 = -5.80890E-05, A8 = 0.00000E + 00, A10 = 0.00000E + 00
[Variable interval data]
Wide angle Medium telephoto f = 5.9438 11.0000 28.1140
d4 = 16.6142 7.1776 1.0000
d12 = 3.6002 8.5886 26.7527
d14 = 4.2706 4.4044 1.8840
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 -13.7293
G2 5 11.09162
G3 13 27.99903
[Conditional value]
Conditional expression (1) (ft × Dt12) / (fw × Dw12) = 0.2845
Conditional expression (2) | R31 / R41 | = 1.3951
Conditional expression (3) D2 / f2 = 0.5287
Conditional expression (4) f1 / f11 = 1.8889
Conditional expression (5) TLw / (fw × ft) ^1/2 = 2.9266
Conditional expression (6) f12 / fw = 3.0321
Conditional expression (7) f2 / ft = 0.3945
Conditional expression (8) f3 / ft = 0.9959
Conditional expression (9) D1 / (− f1) = 0.3047
Conditional expression (10) (D1 + D2 + D3) /ft=0.4107

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied.

  4A to 4C are graphs showing various aberrations of the zoom lens ZL according to the second example. That is, FIG. 4A is a diagram of various aberrations when focusing at infinity in the wide-angle end state (f = 5.94 mm), and FIG. 4B is infinite in the intermediate focal length state (f = 11.00 mm). FIG. 4C is a diagram of various aberrations at the time of focusing on infinity in the telephoto end state (f = 28.11 mm). From the respective aberration diagrams, it can be seen that in the second example, various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and the optical performance is excellent. As a result, by mounting the zoom lens ZL of the second embodiment, excellent optical performance can be ensured also in the digital still camera 1.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a diagram illustrating the configuration and zoom trajectory of the zoom lens according to the third example. The zoom lens of the third embodiment has the same configuration as that of the zoom lens of the first embodiment except for the position of the aspherical surface. Description is omitted. In the third example, the lens surfaces on both sides of the negative meniscus lens L11 of the first lens group G1 are aspheric, and the lens surfaces on both sides of the first positive meniscus lens L21 are aspheric. The object-side lens surface of the third positive meniscus lens L24 is aspheric.

  Table 3 below shows specifications in the third embodiment. The surface numbers 1 to 16 in Table 3 correspond to the surfaces 1 to 16 in FIG. 5, and the group numbers G1 to G3 in Table 3 correspond to the lens groups G1 to G3 in FIG. In the third embodiment, the lens surfaces of the first surface, the second surface, the fifth surface, the sixth surface, and the tenth surface are formed in an aspherical shape.

(Table 3)
[Overall specifications]
Zoom ratio = 4.73
Wide-angle middle telephoto f = 5.98 11.06 28.29
FNO = 3.63 4.51 5.37
ω = 35.66 20.34 5.37
Y = 4.05 4.05 4.05
TL = 38.07838 33.76591 43.20171
Bf = 0.6 0.6 0.6
[Lens specifications]
Surface number r d nd νd
1 * 66.2886 0.8000 1.851350 40.10
2 * 5.8611 1.7832
3 9.5724 1.6000 1.922860 20.88
4 19.1544 (d4)
5 * 7.1596 1.6000 1.497820 82.56
6 * 179.3700 0.1000
7 4.6250 1.8000 1.755000 52.32
8 15.6413 0.5000 1.903660 31.31
9 3.5314 0.8642
10 * 12.0069 1.0000 1.693500 53.22
11 90.0887 0.2000
12 ∞ (d12) Aperture S
13 59.8374 1.5000 1.603001 65.44
14 -23.3192 (d14)
15 ∞ 1.0000 1.516330 64.14
16 ∞ (Bf)
[Aspherical data]
First side κ =
1.0000, A4 = -3.55890E-05, A6 = 6.12330E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
2nd surface κ = 0.6779, A4 = -1.83340E-04, A6 = -6.05370E-06, A8 = 1.73680E-07, A10 = -4.38570E-09
5th surface κ = 0.0269, A4 = -2.71670E-04, A6 = -9.29090E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = 8.0000, A4 = -6.17480E-04, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
10th surface κ = -6.2832, A4 = -1.15820E-04, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
[Variable interval data]
Wide-angle middle telephoto f = 5.9782 11.0631 28.2912
d4 = 16.6141 7.1776 1.0000
d12 = 4.0487 9.0371 27.2011
d14 = 4.0681 4.2039 1.6532
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 -13.72671
G2 5 11.092
G3 13 28.01743
[Conditional value]
Conditional expression (1) (ft × Dt12) / (fw × Dw12) = 0.2848
Conditional expression (2) | R31 / R41 | = 1.54802
Conditional expression (3) D2 / f2 = 0.5287
Conditional expression (4) f1 / f11 = 1.8065
Conditional expression (5) TLw / (fw × ft) ^1/2 = 2.9280
Conditional expression (6) f12 / fw = 3.2110
Conditional expression (7) f2 / ft = 0.3921
Conditional expression (8) f3 / ft = 0.9903
Conditional expression (9) D1 / (− f1) = 0.3048
Conditional expression (10) (D1 + D2 + D3) /ft=0.4082

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (10) are satisfied.

  6A to 6C are graphs showing various aberrations of the zoom lens ZL according to the third example. That is, FIG. 6A is a diagram showing various aberrations when focusing on infinity in the wide-angle end state (f = 5.98 mm), and FIG. 6B is infinite in the intermediate focal length state (f = 11.06 mm). FIG. 6C is a diagram of various aberrations at the time of focusing on infinity in the telephoto end state (f = 28.29 mm). From the aberration diagrams, it can be seen that in the third example, various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and the optical performance is excellent. As a result, by mounting the zoom lens ZL of the third embodiment, excellent optical performance can be ensured also in the digital still camera 1.

  As described above, according to each embodiment, a zoom lens and an optical apparatus (digital still camera) having an excellent optical performance suitable for a high-pixel electronic image pickup device and having a zoom ratio of about 5 times while reducing a thickness when retracted. ) Can be realized.

  In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

  In each of the above-described embodiments, the three-group configuration is shown as the zoom lens. Further, a configuration in which a lens or a lens group is added to the most object side, or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group indicates a portion having at least one lens separated by an air interval that changes at the time of zooming.

  In addition, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. This focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like). In particular, the third lens group is preferably a focusing lens group.

  In addition, the lens group or the partial lens group is moved so as to have a component in a direction perpendicular to the optical axis, or is rotated (swayed) in the in-plane direction including the optical axis to reduce image blur caused by camera shake. A vibration-proof lens group to be corrected may be used. In particular, it is preferable that at least a part of the second lens group is an anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  The aperture stop is preferably disposed in the vicinity of the second lens group, but the role of the aperture stop may be substituted by a lens frame without providing a member as an aperture stop.

  Each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

  In addition, the zoom lens (variable magnification optical system) of the present embodiment has a magnification ratio of about 4.5 to 6.0.

  In the zoom lens (variable magnification optical system) of the present embodiment, it is preferable that the first lens group has one positive lens component and one negative lens component. At this time, it is preferable that the lens components are arranged in order of negative / positive in order from the object side with an air gap interposed therebetween. The second lens group preferably has two positive lens components and one negative lens component. At this time, it is preferable to arrange the lens components in the order of positive / positive / negative (or positive / positive / negative / positive) in order from the object side with an air gap interposed therebetween. The third lens group preferably has one positive lens component.

It is a figure which shows the structure and zoom track of the zoom lens which concerns on 1st Example. (A) is various aberration diagrams at the time of focusing on infinity in the wide angle end state in the first embodiment, (b) is a diagram of various aberrations at the time of focusing on infinity in the intermediate focal length state, (c) These are various aberration diagrams when focusing on infinity in the telephoto end state. It is a figure which shows the structure of a zoom lens and zoom trajectory which concern on 2nd Example. (A) is an aberration diagram at the time of infinity focusing in the wide-angle end state in the second embodiment, (b) is an aberration diagram at the time of focusing at infinity in the intermediate focal length state, (c) These are various aberration diagrams when focusing on infinity in the telephoto end state. It is a figure which shows the structure and zoom orbit of the zoom lens which concerns on 3rd Example. (A) is an aberration diagram at the time of infinity focusing in the wide angle end state in the third embodiment, (b) is an aberration diagram at the time of focusing at infinity in the intermediate focal length state, (c) These are various aberration diagrams when focusing on infinity in the telephoto end state. (A) is a front view of a digital still camera, (b) is a rear view of the digital still camera, and (c) is a cross-sectional view taken along arrow AA ′ in FIG. It is a flowchart which shows the manufacturing method of a zoom lens.

Explanation of symbols

CAM digital still camera (optical equipment)
ZL Zoom lens G1 First lens group G2 Second lens group G3 Third lens group S Aperture I Image plane L11 Negative meniscus lens (negative lens) L12 Positive meniscus lens (positive lens)
L21 First positive meniscus lens L22 Second positive meniscus lens L23 Negative lens L24 Third positive meniscus lens L31 Positive lens

Claims (14)

A zoom having a first lens group having negative refracting power, a second lens group having positive refracting power, and a third lens group having positive refracting power, arranged in order from the object side along the optical axis. In the lens,
The first lens group includes one negative lens and one positive lens arranged in order from the object side along the optical axis.
The second lens group includes a first positive lens, a second positive lens, a negative lens, and a third positive lens arranged in order from the object side along the optical axis.
The third lens group includes one positive lens,
The focal length in the telephoto end state of the zoom lens is ft, the focal length in the wide-angle end state of the zoom lens is fw, and the distance on the optical axis between the first lens group and the second lens group in the telephoto end state Is Dt12, and the distance on the optical axis between the first lens group and the second lens group in the wide-angle end state is Dw12, the following expression 0.15 <(ft × Dt12) / (fw × Dw12) < 0.30
When the radius of curvature of the object-side lens surface of the first positive lens is R31 and the radius of curvature of the object-side lens surface of the second positive lens is R41, the following formula 0.5 <| R31 / R41 | <2.0
A zoom lens that satisfies the following conditions. When the thickness of the second lens group on the optical axis is D2, and the focal length of the second lens group is f2, the following formula is given: 0.4 <D2 / f2 <0.6
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. When the focal length of the first lens group is f1, and the focal length of the negative lens of the first lens group is f11, the following expression 1.80 <f1 / f11 <1.95
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. When the total length of the zoom lens in the wide-angle end state is TLw, the following formula 2.5 <TLw / (fw × ft) ^1/2 <3.0
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.   The zoom lens according to any one of claims 1 to 4, wherein the third positive lens of the second lens group has an aspherical surface. When the focal length of the positive lens of the first lens group is f12, the following formula 2.8 <f12 / fw <3.3
The zoom lens according to any one of claims 1 to 5, wherein the following condition is satisfied. When the focal length of the second lens group is f2, the following expression 0.3 <f2 / ft <0.4
The zoom lens according to claim 1, wherein the following condition is satisfied. When the focal length of the third lens group is f3, the following formula 0.9 <f3 / ft <1.1
The zoom lens according to claim 1, wherein the following condition is satisfied. When the thickness on the optical axis of the first lens group is D1 and the focal length of the first lens group is f1, the following expression 0.10 <D1 / (− f1) <0.35
The zoom lens according to claim 1, wherein the following condition is satisfied. When the thickness on the optical axis of the first lens group is D1, the thickness on the optical axis of the second lens group is D2, and the thickness on the optical axis of the third lens group is D3, 0.40 <(D1 + D2 + D3) / ft <0.43
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.   The first lens group includes one negative meniscus lens having a convex surface facing the object side and one positive meniscus lens having a convex surface facing the object side, which are arranged in order from the object side along the optical axis. The zoom lens according to claim 1, wherein the zoom lens is a zoom lens.   At the time of zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases and the distance between the second lens group and the third lens group increases. The zoom lens according to claim 1, wherein: In an optical apparatus having a zoom lens that forms an image of an object on a predetermined surface,
An optical apparatus, wherein the zoom lens is the zoom lens according to any one of claims 1 to 12. A zoom lens in which a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged in this order from the object side along the optical axis. In the manufacturing method of
In order from the object side along the optical axis, one negative lens and one positive lens are arranged to constitute the first lens group,
In order from the object side along the optical axis, a first positive lens, a second positive lens, a negative lens, and a third positive lens are arranged to constitute the second lens group,
A positive lens is arranged to form the third lens group,
The focal length in the telephoto end state of the zoom lens is ft, the focal length in the wide-angle end state of the zoom lens is fw, and the distance on the optical axis between the first lens group and the second lens group in the telephoto end state Is Dt12, and the distance on the optical axis between the first lens group and the second lens group in the wide-angle end state is Dw12, the following expression 0.15 <(ft × Dt12) / (fw × Dw12) < 0.30
When the radius of curvature of the object-side lens surface of the first positive lens is R31 and the radius of curvature of the object-side lens surface of the second positive lens is R41, the following formula 0.5 <| R31 / R41 | <2.0
A zoom lens manufacturing method characterized by satisfying the following conditions:

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