JP2010117532A - Zoom lens, optical equipment, and method for manufacturing zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens that is compact and has high optical performance. <P>SOLUTION: The zoom lens ZL includes, in order from an object side along an optical axis: 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. When zooming from the wide-angle end to the tele-photo end, the interval between the first and second lens groups G1 and G2 and the interval between the second and third lens groups G2 and G3 change. In the zoom lens ZL, if the focal length of the zoom lens ZL at the wide angle end is fw, the interval on the optical axis between the second and third lens groups G2 and G3 at the wide angle end is Dw23, the focal length of the zoom lens ZL at the tele-photo end is ft, and the entire length of the zoom lens ZL at the wide angle end is TLw, a condition expressed by 2.4<(ft<SP>2</SP>×Dw23)/(fw<SP>2</SP>×TLw)<4.0 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, in a photographing apparatus (camera) such as a digital still camera or a digital video camera using a solid-state image sensor, the performance of the apparatus and the downsizing of the apparatus are rapidly progressing. In these photographing apparatuses, a zoom lens is generally used as an imaging lens, and the photographer can easily perform photographing at an angle of view optimum for photographing conditions. At present, these zoom lenses are strongly required to have a wide angle and high zoom ratio. For example, an example in which a zoom lens having a field angle of 70 to 80 degrees or more in a wide-angle end state and capable of sufficient telephoto shooting is described in Example 2 of JP-A-2006-208890. .
JP 2006-208890 A

  However, these conventional zoom lenses have a problem that the aberration correction is insufficient and a good imaging performance cannot be obtained.

  The present invention has been made in view of such problems, and an object thereof is to provide a zoom lens, an optical apparatus, and a zoom lens manufacturing method that are compact and have high optical performance.

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, and 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 and the second lens group In the zoom lens configured such that the distance between the zoom lens and the third lens group changes, the focal length in the wide-angle end state of the zoom lens is fw, and the second lens group and the third lens group in the wide-angle end state The distance on the optical axis is Dw23, the focal length of the zoom lens in the telephoto end state is ft, and the total length of the zoom lens in the wide-angle end state is TLw. 2.4 <(ft ² × Dw23) / (fw ² × Lw) <4.0
The conditions are satisfied.

In the zoom lens described above, when the focal length of the first lens group is f1, the following formula 1.9 <ft / (− f1) <2.3
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the maximum image height of the zoom lens is Ymax, the following expression 1.7 <(fw × TLw) / (ft × Ymax) <2.0
It is preferable to satisfy the following conditions.

In the zoom lens described above, when the refractive index of the negative lens having the highest refractive index with respect to the d-line in the second lens group is Ndn and the Abbe number of the negative lens is νdn, the following expression 3 .15 <Ndn + (0.05 × νdn) <3.60
And satisfying the following formula: 1.8 <Ndn <2.5
It is preferable to satisfy the following conditions.

In the zoom lens described above, the third lens group includes one positive lens, and the paraxial radius of curvature of the object-side lens surface of the positive lens is Ra, and the image-side lens surface of the positive lens is When the paraxial radius of curvature is Rb, the following formula: −0.4 <(Rb + Ra) / (Rb−Ra) <1.0
It is preferable to satisfy the following conditions.

  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 preferable that at least the first lens group and the second lens group move so that the distance from the group increases.

  In the zoom lens described above, it is preferable that the first lens group includes one negative lens and one positive lens arranged in order from the object side along the optical axis.

  In the zoom lens described above, it is preferable that the lens located closest to the object side in the first lens group has an aspherical surface.

  In the zoom lens described above, it is preferable that the second lens group includes two positive lenses and one negative lens arranged in order from the object side along the optical axis.

  In the zoom lens described above, it is preferable that one positive lens and one negative lens are arranged in order from the image side along the optical axis in the second lens group.

  In the zoom lens described above, the second lens group includes two positive lenses, one negative lens, and one positive lens arranged in order from the object side along the optical axis. Is preferred.

  In the zoom lens described above, it is preferable that the lens located closest to the object side in the second lens group has an aspherical surface.

  In the zoom lens described above, it is preferable that the third lens group is fixed on the optical axis at the time of zooming from the wide-angle end state to the telephoto end state.

  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 a method of manufacturing a zoom lens in which a third lens group having power is arranged, the distance between the first lens group and the second lens group and the second lens during zooming from the wide-angle end state to the telephoto end state The distance between the lens group and the third lens group is changed, and the focal length in the wide-angle end state of the zoom lens is fw, and the light from the second lens group and the third lens group in the wide-angle end state When the distance on the axis is Dw23, the focal length of the zoom lens in the telephoto end state is ft, and the total length of the zoom lens in the wide-angle end state is TLw, the following formula 2.4 <(ft ² × Dw23) / (fw ² × TLw <4.0
To meet the requirements of

  According to the present invention, a compact and high optical performance can be obtained.

  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, and a first lens group having a positive refractive power, which are arranged in order from the object side along the optical axis. This is a negative preceding type zoom lens having three lens groups G3. The zoom lens ZL is moved by moving the first lens group G1 and the second lens group G2 along the optical axis during zooming from the wide-angle end state to the telephoto end state (for example, 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 second lens group G2 is a zoom unit and a master lens group, and the first lens group G1 is a compensator group. The third lens group G3 optimizes the exit pupil position of the entire zoom lens system with respect to the image sensor C, and corrects the remaining aberration that cannot be corrected by the first lens group G1 and the second lens group G2. .

  In order to simultaneously perform widening of the angle and high zooming using the zoom lens ZL having such a configuration, it is necessary to satisfy various conditions. In particular, it is difficult to perform good aberration correction unless the configuration of each lens group, the refractive power of each lens, the position of the aspherical lens, and the like are set appropriately. On the other hand, from the practical viewpoint of the zoom lens, it is necessary to sufficiently reduce the size of the entire zoom lens.

  Therefore, in order to achieve the miniaturization and high performance of the zoom lens ZL, the focal length in the wide-angle end state of the zoom lens ZL is fw, and the light from the second lens group G2 and the third lens group G3 in the wide-angle end state When the axial distance is Dw23, the focal length of the zoom lens ZL in the telephoto end state is ft, and the total length of the zoom lens ZL in the wide-angle end state is TLw, the condition expressed by the following conditional expression (1) is satisfied. It is preferable to satisfy. In this way, the overall length of the zoom lens ZL can be reduced, and each aberration can be corrected well. Therefore, the zoom lens ZL having a compact and high optical performance, and an optical apparatus ( Digital still camera CAM) can be obtained.

2.4 <(ft ² × Dw23) / (fw ² × TLw) <4.0 (1)

  Conditional expression (1) is a conditional expression for defining an appropriate distance between the second lens group G2 and the third lens group G3 with respect to the zoom ratio. When the condition is lower than the lower limit value of the conditional expression (1), it is not preferable because it is difficult to correct the field curvature in the wide-angle end state. On the other hand, when the condition exceeds the upper limit value of conditional expression (1), it is difficult to correct spherical aberration in the telephoto end state, which is not preferable.

  By setting the lower limit value of conditional expression (1) to 2.55, or the upper limit value of conditional expression (1) to 3.80, the effect of the present application can be exhibited better. Furthermore, by setting the lower limit value of conditional expression (1) to 2.70 or the upper limit value of conditional expression (1) to 3.60, the effects 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 (2) is satisfied when the focal length of the first lens group G1 is f1.

  1.9 <ft / (− f1) <2.3 (2)

  Conditional expression (2) is a conditional expression for defining an appropriate refractive power of the first lens group G1. When the condition is less than the lower limit value of the conditional expression (2), the front lens diameter in the wide-angle end state increases, and it becomes difficult to correct distortion aberration and field curvature in the wide-angle end state. On the other hand, when the condition exceeds the upper limit value of the conditional expression (2), it is difficult to correct the spherical aberration in the telephoto end state.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (2) to 1.94 or the upper limit value of conditional expression (2) to 2.23. Furthermore, by setting the lower limit value of conditional expression (2) to 1.98 or the upper limit value of conditional expression (2) to 2.17, the effects 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 (3) is satisfied, where Ymax is the maximum image height of the zoom lens ZL.

  1.7 <(fw × TLw) / (ft × Ymax) <2.0 (3)

  Conditional expression (3) is a conditional expression for defining the total length of the zoom lens appropriate for the zoom ratio. When the condition is lower than the lower limit value of the conditional expression (3), it is not preferable because it becomes difficult to correct spherical aberration in the telephoto end state. On the other hand, a condition that exceeds the upper limit value of conditional expression (3) is not preferable because it is difficult to correct coma in the intermediate focal length state.

  In addition, the effect of this application can be exhibited more favorably by setting the lower limit value of conditional expression (3) to 1.75 or the upper limit value of conditional expression (3) to 1.95. Furthermore, by setting the lower limit value of conditional expression (3) to 1.80 or the upper limit value of conditional expression (3) to 1.93, the effects of the present application can be maximized.

  In such a zoom lens ZL, when the refractive index for the d-line of the negative lens having the highest refractive index for the d-line in the second lens group G2 is Ndn and the Abbe number of the negative lens is νdn, It is preferable that the conditions expressed by the conditional expressions (4) and (5) are satisfied.

3.15 <Ndn + (0.05 × νdn) <3.60 (4)
1.8 <Ndn <2.5 (5)

  Conditional expression (4) is a conditional expression for satisfactorily correcting the difference in spherical aberration depending on the wavelength in the telephoto end state. When the condition is lower than the lower limit value of the conditional expression (4), the spherical aberration on the short wavelength side with respect to the d line is remarkably insufficiently corrected, which is not preferable. On the other hand, when the condition exceeds the upper limit value of the conditional expression (4), the spherical aberration on the short wavelength side with respect to the d-line is significantly overcorrected, which is not preferable.

  Conditional expression (5) is a conditional expression for defining an appropriate refractive index of the negative lens in the second lens group G2. When the condition is lower than the lower limit value of the conditional expression (5), it is not preferable because it is difficult to correct the sagittal field curvature in the wide-angle end state. On the other hand, when the condition exceeds the upper limit value of the conditional expression (5), the Petzval sum is remarkably increased, which makes it difficult to correct curvature of field in the intermediate focal length state, which is not preferable.

  By setting the lower limit value of conditional expression (4) to 3.20, or the upper limit value of conditional expression (4) to 3.55, the effects of the present application can be exhibited better. Furthermore, by setting the lower limit value of conditional expression (4) to 3.25 or the upper limit value of conditional expression (4) to 3.50, the effects of the present application can be maximized.

  Further, when the lower limit value of conditional expression (5) is 1.85, or the upper limit value of conditional expression (5) is 2.35, the effect of the present application can be exhibited more satisfactorily. Furthermore, by setting the lower limit value of conditional expression (5) to 1.90 or the upper limit value of conditional expression (5) to 2.20, the effects of the present application can be maximized.

  In such a zoom lens ZL, the third lens group G3 is composed of one positive lens, and the paraxial radius of curvature of the object-side lens surface of the positive lens is Ra, and the image-side lens of the positive lens. When the paraxial radius of curvature of the surface is Rb, it is preferable that the condition represented by the following conditional expression (6) is satisfied.

  −0.4 <(Rb + Ra) / (Rb−Ra) <1.0 (6)

  Conditional expression (6) is a conditional expression for defining an appropriate shape of the positive lens in the third lens group G3. When the condition is lower than the lower limit value of the conditional expression (6), it is difficult to simultaneously correct distortion and astigmatism in the wide-angle end state, which is not preferable. On the other hand, when the condition exceeds the upper limit value of the conditional expression (6), it is difficult to correct the coma aberration 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 (6) to −0.25 or the upper limit value of conditional expression (6) to 0.8. Furthermore, by setting the lower limit value of conditional expression (6) to −0.1 or the upper limit value of conditional expression (6) to 0.6, the effect of the present application can be maximized.

  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 at least the first lens group G1 and the second lens group G2 move so that the distance from the lens group G3 increases.

  In such a zoom lens ZL, it is preferable that the first lens group G1 includes one negative lens and one positive lens arranged in order from the object side along the optical axis. By configuring the first lens group G1 as described above, 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.

  In such a zoom lens ZL, it is preferable that the lens located closest to the object side in the first lens group G1 has an aspherical surface. By making the most object side lens in the first lens group G1 an aspherical lens, distortion and coma aberration in the wide-angle end state and coma aberration in the telephoto end state can be corrected more satisfactorily.

  In such a zoom lens ZL, the second lens group G2 preferably includes two positive lenses and one negative lens arranged in order from the object side along the optical axis. With this configuration, the principal point of the second lens group G2 can be moved to the object side, and contact between the first lens group G1 and the second lens group G2 in the telephoto end state is avoided. In addition to this, spherical aberration can be corrected well.

  In such a zoom lens ZL, it is preferable that one positive lens and one negative lens are arranged in order from the image side along the optical axis in the second lens group G2. With such a configuration, it is possible to satisfactorily correct field curvature in the wide-angle end state.

  Therefore, the second lens group G2 may be composed of two positive lenses, one negative lens, and one positive lens arranged in order from the object side along the optical axis. With such a configuration, as described above, in addition to avoiding contact between the first lens group G1 and the second lens group G2 in the telephoto end state, it is possible to satisfactorily correct spherical aberration. Furthermore, it is possible to satisfactorily correct the field curvature in the wide-angle end state.

  In such a zoom lens ZL, it is preferable that the lens located closest to the object side in the second lens group G2 has an aspherical surface. By making the most object side lens surface of the second lens group G2 aspherical, spherical aberration can be corrected more favorably.

  In such a zoom lens ZL, it is preferable that the third lens group G3 is fixed on the optical axis at the time of zooming from the wide-angle end state to the telephoto end state. By fixing the third lens group G3, it is possible to satisfactorily correct lateral chromatic aberration in the telephoto end state.

  In the wide-angle zoom lens ZL of the present embodiment, focusing from an object at infinity to a close object can be performed by extending the first lens group G1 or the third lens group G3 to the object side. However, since the method of extending the first lens group G1 tends to cause a reduction in the amount of light at the periphery of the screen at the time of close-up shooting, it is more preferable to perform by extending the third lens group G3 to the object side.

  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 lens group for performing zooming (in this embodiment, the first lens group G1 and the second lens group G2) moves along the optical axis direction. A focusing operation in which a lens group (in this embodiment, the third lens group G3) that focuses on a short-distance object moves along the optical axis direction, at least some of the lenses have a component perpendicular to the optical axis. For example, a camera shake correction operation that moves as if it is held. In the present embodiment, the first lens group G1 and the second lens group G2 move along the optical axis during zooming from the wide-angle end state to the telephoto end state, so that the first lens group G1 is moved. The distance between the second lens group G2 decreases and the distance between the second lens group G2 and the third lens group G3 increases. In addition, the confirmation order of various operations is arbitrary. According to such a manufacturing method, a zoom lens ZL having a compact and high optical performance can be obtained.

(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. It is composed of a group G2 and a third lens group G3 having a positive refractive power. When zooming from the wide-angle end state to the telephoto end state, the first lens group G1 and the second lens group G2 move along the optical axis, so that the first lens group G1 and the second lens group G2 The distance between the 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 to the object side, the second lens group G2 monotonously moves to the object side, and the third lens group G3 is fixed.

  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 surface on the image side of the lens L11 is an aspherical surface. The second lens group G2 is arranged in order from the object side along the optical axis, a positive meniscus lens L21 having a convex surface facing the object side, a biconvex positive lens L22, a biconcave negative lens L23, It is composed of a biconvex positive lens L24, and the object-side lens surface of the positive meniscus lens L21 is aspheric. The biconvex positive lens L22 and the biconcave negative lens L23 are preferably cemented lenses. The third lens group G3 includes a single positive lens L31, and focusing from an object at infinity to an object at a finite distance is performed by moving the third lens group G3 along the optical axis.

  An F-number determining member S composed of a sheet material, a lens frame, and the like is provided on the image side from the vertex on the optical axis of the positive meniscus lens L21 of the second lens group G2, and changes from the wide angle end state to the telephoto end state. During zooming, the zoom lens moves together with the second lens group G2. 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 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 indicates a focal length, FNO indicates an F number, 2ω indicates an angle of view (unit is “°”), and Ymax indicates a maximum image height. 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 on the optical axis of the lens surfaces, nd is the d-line (wavelength λ 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, and is along the optical axis from the tangent plane of each aspheric surface to each aspheric surface at height y. The distance (sag amount) is S (y), the paraxial radius of curvature (the radius of curvature of the reference sphere) is R, the conic constant is κ, and the aspherical coefficient of the nth order (n = 4, 6, 8, 10). Is represented by the following conditional expression (7). In each example, the secondary aspherical coefficient A2 is 0, and the description is omitted. In [Aspherical data], “En” indicates “× 10 ⁻ⁿ ”.

S (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 ... (7)

  In [variable interval data], d4 is the axial air interval between the first lens group G1 and the second lens group G2 (F-number determining member S), and d12 is the second lens group G2 and the third lens group G3. , D14 is the axial air distance between the third lens group G3 and the filter group FL, f is the focal length, TL is the total lens length, and Bf is the back focus. These on-axis air intervals (d4, d12, d14), the focal length f, the total lens length TL, and the like 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 18 in Table 1 correspond to the surfaces 1 to 18 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 second and sixth lens surfaces are aspherical.

(Table 1)
[Overall specifications]
Zoom ratio = 4.72
f = 5.15-24.30
FNO = 2.74 ~ 6.99
2ω = 77.14-18.16
Ymax = 3.9
[Lens specifications]
Surface number r d nd νd
1 35.1579 0.9500 1.84973 40.30
2 * 4.8867 2.3000
3 8.9145 1.5500 1.92286 20.88
4 16.5874 (d4)
5 ∞ -0.5000 F number determining member S
6 * 5.8500 1.4000 1.77377 47.18
7 45.3904 0.1000
8 5.2405 1.6000 1.71999 50.24
9 -113.6153 0.4000 2.00330 28.27
10 3.5525 0.5700
11 19.2838 1.1500 1.65844 50.88
12 -20.0191 (d12)
13 19.0671 1.5000 1.60300 65.47
14 -41.0965 (d14)
15 ∞ 0.2100 1.51680 64.12
16 ∞ 0.2900
17 ∞ 0.5000 1.51680 64.12
18 ∞ (Bf)
[Aspherical data]
2nd surface κ = 0.1871, A4 = 2.54930E-04, A6 = 3.99050E-06, A8 = -5.58790E-08, A10 = 7.87310E-10
6th surface κ = 0.0734, A4 = 3.54380E-04, A6 = 3.04510E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state
Focusing at infinity Focusing at infinity Focusing at infinity f = 5.15 11.20 24.30
d4 = 15.3894 5.3891 0.8000
d12 = 5.0523 11.3904 25.1141
d14 = 2.2303 2.2303 2.2303
Bf = 0.6000 0.6000 0.6000
TL = 35.2920 31.6297 40.7643
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 -11.84
G2 6 9.99
G3 13 21.80
[Conditional value]
Conditional expression (1) (ft ² × Dw23) / (fw ² × TLw) = 3.1872
Conditional expression (2) ft / (− f1) = 2.0526
Conditional expression (3) (fw × TLw) / (ft × Ymax) = 1.9178
Conditional expression (4) Ndn + (0.05 × νdn) = 3.417
Conditional expression (5) Ndn = 2.003
Conditional expression (6) (Rb + Ra) / (Rb-Ra) = 0.3662

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (6) 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 of various aberrations when focusing at infinity in the wide-angle end state (f = 5.15 mm), and FIG. 2B is infinite in the intermediate focal length state (f = 111.20 mm). FIG. 2C is a diagram of various aberrations at the time of focusing on infinity in the telephoto end state (f = 24.30 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 indicates the aberration at the d-line (λ = 587.6 nm), and g indicates the aberration at the g-line (λ = 435.8 nm). In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane.

  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 lens surfaces on both sides of the negative meniscus lens L11 of the first lens group G1 are aspheric, and the object-side lens surfaces of the positive meniscus lens L21 of the second lens group G2 are aspheric. It has become.

  Table 2 below shows specifications in the second embodiment. The surface numbers 1 to 18 in Table 2 correspond to the surfaces 1 to 18 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 embodiment, the first, second, and sixth lens surfaces are aspherical.

(Table 2)
[Overall specifications]
Zoom ratio = 4.72
f = 5.15-24.30
FNO = 2.70-6.96
2ω = 77.14-18.16
Ymax = 3.9
[Lens specifications]
Surface number r d nd νd
1 * 27.8720 0.9500 1.88300 40.77
2 * 4.7990 2.3000
3 8.6689 1.5000 2.00170 20.65
4 14.5829 (d4)
5 ∞ -0.5000 F number determining member S
6 * 6.1113 1.3500 1.77377 47.18
7 45.9826 0.1000
8 5.0297 1.7000 1.71999 50.24
9 -60.1923 0.4000 2.00330 28.27
10 3.5398 0.5700
11 17.9856 1.1500 1.65844 50.88
12 -18.6844 (d12)
13 19.3972 1.5000 1.60300 65.47
14 -40.7488 (d14)
15 ∞ 0.2100 1.51680 64.12
16 ∞ 0.2900
17 ∞ 0.5000 1.51680 64.12
18 ∞ (Bf)
[Aspherical data]
1st surface κ = -2.0543, A4 = -1.02800E-05, A6 = 2.65770E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
2nd surface κ = 0.1671, A4 = 2.87890E-04, A6 = 5.79920E-06, A8 = -1.23600E-07, A10 = 2.97850E-09
6th surface κ = 0.1791, A4 = 2.76980E-04, A6 = 2.30580E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state
Focusing at infinity Focusing at infinity Focusing at infinity f = 5.15 11.20 24.30
d4 = 14.6119 5.1445 0.8000
d12 = 4.8040 11.1758 24.9728
d14 = 2.2919 2.2919 2.2919
Bf = 0.6000 0.6000 0.6000
TL = 34.3278 31.2323 40.6846
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 -11.50
G2 6 9.75
G3 13 22.00
[Conditional value]
Conditional expression (1) (ft ² × Dw23) / (fw ² × TLw) = 3.1157
Conditional expression (2) ft / (− f1) = 2.1130
Conditional expression (3) (fw × TLw) / (ft × Ymax) = 1.8654
Conditional expression (4) Ndn + (0.05 × νdn) = 3.417
Conditional expression (5) Ndn = 2.003
Conditional expression (6) (Rb + Ra) / (Rb-Ra) = 0.3550

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (6) 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 = 5.15 mm), and FIG. 4B is infinite in the intermediate focal length state (f = 111.20 mm). FIG. 4C is a diagram of various aberrations at the time of focusing on infinity in the telephoto end state (f = 24.30 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 object-side lens surfaces of the positive meniscus lens L21 of the second lens group G2 are aspheric. It has become.

  Table 3 below shows specifications in the third embodiment. The surface numbers 1 to 18 in Table 3 correspond to the surfaces 1 to 18 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, and the sixth surface are formed in an aspheric shape.

(Table 3)
[Overall specifications]
Zoom ratio = 4.72
f = 5.15-24.30
FNO = 2.70-6.99
2ω = 78.36-18.30
Ymax = 3.9
[Lens specifications]
Surface number r d nd νd
1 * 23.3678 0.9500 1.88300 40.77
2 * 4.7898 2.3000
3 8.9009 1.5000 2.00170 20.65
4 14.7464 (d4)
5 ∞ -0.5000 F number determining member S
6 * 5.7361 1.4500 1.77377 47.18
7 443.6780 0.1000
8 5.0767 1.5500 1.69350 53.22
9 -74.6228 0.4000 2.00330 28.27
10 3.4025 0.5700
11 22.3949 1.1000 1.63930 44.89
12 -22.5014 (d12)
13 28.0674 1.5500 1.61800 63.38
14 -23.7357 (d14)
15 ∞ 0.2100 1.51680 64.12
16 ∞ 0.2900
17 ∞ 0.5000 1.51680 64.12
18 ∞ (Bf)
[Aspherical data]
1st surface κ = -99.0000, A4 = 2.90520E-05, A6 = 6.39520E-06, A8 = -1.40940E-07, A10 = 9.87060E-10
2nd surface κ = -2.1845, A4 = 1.86910E-03, A6 = -2.40760E-05, A8 = 8.48860E-07, A10 = -1.21150E-08
6th surface κ = -1.2760, A4 = 1.19920E-03, A6 = -1.13680E-05, A8 = 0.00000E + 00, A10 = 0.00000E + 00
[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state
Focusing at infinity Focusing at infinity Focusing at infinity f = 5.15 11.20 24.30
d4 = 14.6976 5.1715 0.8000
d12 = 4.1576 10.2330 23.3880
d14 = 2.3545 2.3545 2.3545
Bf = 0.6000 0.6000 0.6000
TL = 33.7797 30.3290 39.1125
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 -11.85
G2 6 9.55
G3 13 21.05
[Conditional value]
Conditional expression (1) (ft ² × Dw23) / (fw ² × TLw) = 2.7400
Conditional expression (2) ft / (− f1) = 2.0506
Conditional expression (3) (fw × TLw) / (ft × Ymax) = 1.8358
Conditional expression (4) Ndn + (0.05 × νdn) = 3.417
Conditional expression (5) Ndn = 2.003
Conditional expression (6) (Rb + Ra) / (Rb-Ra) =-0.0836

  Thus, in this embodiment, it can be seen that all the conditional expressions (1) to (6) 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 = 5.15 mm), and FIG. 6B is infinite in the intermediate focal length state (f = 111.20 mm). FIG. 6C is a diagram of various aberrations at the time of focusing on infinity in the telephoto end state (f = 24.30 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, it is possible to realize a wide-angle zoom lens and an optical apparatus (digital still camera) having excellent optical performance with a zoom ratio of about 5 times while reducing the thickness when retracted. .

  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.

  The zoom lens ZL of the present embodiment has a zoom ratio of about 4.5 to 6.0.

  The first lens group G1 preferably has one positive lens component and at least one negative lens component. At this time, it is preferable that the first lens group G1 includes a negative lens component and a positive lens component in order from the object side. The second lens group G2 preferably includes two positive lens components and at least one negative lens component. At this time, in the second lens group G2, two positive lens components and one negative lens component are arranged in order from the object side, or two positive lens components, one negative lens component, and 1 It is preferable to arrange two positive lens components. The third lens group G3 preferably has at least 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 F-number determining member I Image plane L11 Negative meniscus lens (negative lens) L12 Positive meniscus lens (positive lens)
L21 Positive meniscus lens (positive lens) L22 Positive lens L23 Negative lens L24 Positive lens L31 Positive lens

Claims (15)

A first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, which are arranged in order from the object side along the optical axis. The distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group change during zooming from the wide-angle end state to the telephoto end state. Zoom lens
The focal length in the wide-angle end state of the zoom lens is fw, the distance on the optical axis between the second lens group and the third lens group in the wide-angle end state is Dw23, and the focal length in the telephoto end state of the zoom lens. Is ft, and the total length of the zoom lens in the wide-angle end state is TLw, the following formula 2.4 <(ft ² × Dw23) / (fw ² × TLw) <4.0
A zoom lens that satisfies the following conditions. When the focal length of the first lens unit is f1, the following formula 1.9 <ft / (− f1) <2.3
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. When the maximum image height of the zoom lens is Ymax, the following expression 1.7 <(fw × TLw) / (ft × Ymax) <2.0
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. When the refractive index of the negative lens having the highest refractive index with respect to the d-line in the second lens group is Ndn and the Abbe number of the negative lens is νdn, the following expression 3.15 <Ndn + (0.05 × νdn) <3.60
And satisfying the following formula: 1.8 <Ndn <2.5
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition. The third lens group includes one positive lens, and the paraxial radius of curvature of the object side lens surface of the positive lens is Ra, and the paraxial radius of curvature of the image side lens surface of the positive lens is Rb. When: -0.4 <(Rb + Ra) / (Rb-Ra) <1.0
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.   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 at least the first lens group and the second lens group move.   The first lens group includes one negative lens and one positive lens arranged in order from the object side along the optical axis. The described zoom lens.   The zoom lens according to any one of claims 1 to 7, wherein a lens located closest to the object side in the first lens group has an aspherical surface.   The said 2nd lens group has two positive lenses and one negative lens which were arranged in order from the object side along the optical axis, The any one of Claim 1 to 8 characterized by the above-mentioned. The described zoom lens.   10. The second lens group includes one positive lens and one negative lens arranged in order from the image side along the optical axis. Zoom lens described in 1.   The second lens group is composed of two positive lenses, one negative lens, and one positive lens arranged in order from the object side along the optical axis. The zoom lens according to any one of 10.   The zoom lens according to any one of claims 1 to 11, wherein a lens located closest to the object side in the second lens group has an aspherical surface.   The zoom lens according to any one of claims 1 to 12, wherein the third lens group is fixed on the optical axis during zooming from the wide-angle end state to the telephoto end state. 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 13. 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
The zoom lens is configured to change the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group at the time of zooming from the wide-angle end state to the telephoto end state.
The focal length in the wide-angle end state of the zoom lens is fw, the distance on the optical axis between the second lens group and the third lens group in the wide-angle end state is Dw23, and the focal length in the telephoto end state of the zoom lens. Is ft, and the total length of the zoom lens in the wide-angle end state is TLw, the following formula 2.4 <(ft ² × Dw23) / (fw ² × TLw) <4.0
A zoom lens manufacturing method characterized by satisfying the following conditions:

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