JP2011017773A - Zoom lens, optical apparatus with the same mounted thereon and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra-compact zoom lens that has a wide viewing angle in a wide-angle end state, ensures high image quality, and is suitable for, e.g., a video camera and an electronic still camera using a solid-state imaging device or the like, and to provide an optical apparatus with the zoom lens mounted thereon, and a method for manufacturing the zoom lens.SOLUTION: The zoom lens having an optical element P for bending an optical path includes, in order from an object side along an optical axis: a first lens group G1 having positive refractive power; a second lens group G2 having negative refractive power; a third lens group G3 having positive refractive power; a fourth lens group G4 having positive refractive power; and a fifth lens group G5 having negative refractive power. Provided that the focal length of the first lens group G1 is denoted as fG1 and the focal length of the zoom lens in the wide-angle end state is denoted as fW, the zoom lens satisfies the following conditional inequality: 3.5<fG1/fW<10.0.

Description

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

  Recently, portability of a digital still camera or the like is regarded as important, and in order to reduce the size, thickness, and weight of a camera body, a zoom lens that is a photographing lens has been reduced in size and weight. For example, a zoom lens having an optical element (prism) for bending an optical path at approximately 90 degrees in a part of a lens system has been proposed (see, for example, Patent Document 1). By mounting such a zoom lens on the camera, the lens does not protrude from the camera body when shifting from the retracted state to the used state, and is excellent in portability in the used state. It has also contributed greatly.

JP 2007-304195 A

  However, in the conventional zoom lens, the angle of view at the wide-angle end state is a standard range, so that when the subject is close, the range that the photographer wants to shoot deviates from the angle of view. At this time, if it is difficult for the photographer to move away from the subject, the image height must be increased to widen the angle of view, which may lead to an increase in the size of the entire optical system.

  The present invention has been made in view of such a problem, and is suitable for a video camera or an electronic still camera using a solid-state imaging device or the like, has a wide angle of view at a wide-angle end state, is ultra-compact, and has high image quality. An object of the present invention is to provide a zoom lens, an optical apparatus equipped with the zoom lens, and a manufacturing method.

  In order to achieve such an object, the present invention provides a zoom lens having an optical element for bending an optical path, a first lens group having a positive refractive power, arranged in order from the object side along the optical axis, A second lens group having a negative refractive power; a third lens group having a positive refractive power; a fourth lens group having a positive refractive power; and a fifth lens group having a negative refractive power; When the focal length in the wide-angle end state of the zoom lens is fW and the focal length of the first lens group is fG1, the following expression 3.5 <fG1 / fW <10.0 is satisfied.

  The first lens group and the third lens group are preferably fixed during zooming from the wide-angle end state to the telephoto end state.

  Further, it is preferable that an aperture stop for determining a light beam is disposed between the second lens group and the third lens group.

  The first lens group includes a lens having negative refractive power, an optical element for bending the optical path, and a lens having positive refractive power, which are arranged in order from the object side along the optical axis. It is preferable.

  The second lens group includes a lens having a negative refractive power, a lens having a negative refractive power, and a lens having a positive refractive power, which are arranged in order from the object side along the optical axis. Is preferred.

  In addition, it is preferable that at least one of the fourth lens group and the fifth lens group is composed only of a cemented lens.

  In addition, it is preferable that at least one of the fourth lens group and the fifth lens group is composed only of a cemented lens of a lens having a positive refractive power and a lens having a negative refractive power.

  Further, an optical apparatus of the present invention (for example, the digital still camera 1 in the present embodiment) is equipped with any of the above zoom lenses.

  The present invention also relates to a method of manufacturing a zoom lens having an optical element for folding an optical path, the first lens group having a positive refractive power arranged in order from the object side along the optical axis, and a negative lens A second lens group having a refractive power; a third lens group having a positive refractive power; a fourth lens group having a positive refractive power; and a fifth lens group having a negative refractive power; When the focal length in the wide-angle end state of the lens is fW and the focal length of the first lens group is fG1, the lens barrel is set so as to satisfy the following condition: 3.5 <fG1 / fW <10.0 Install each lens inside and check the operation.

  According to the present invention, it is suitable for a video camera or an electronic still camera using a solid-state imaging device or the like, has a wide angle of view at a wide angle end state, is ultra-compact, and has a high image quality zoom lens, A manufacturing method can be provided.

FIG. 2 is a cross-sectional view and a zoom locus illustrating a configuration of a zoom lens according to Example 1, where (W) is an infinitely focused state in a wide-angle end state, and (M) is an infinitely focused state in an intermediate focal length state. (T) indicates the infinite focus state in the telephoto end state. FIG. 3A is a diagram illustrating various aberrations of the zoom lens according to the first example, FIG. 9A is a diagram illustrating various aberrations in an infinite focus state in a wide-angle end state, and FIG. 9B is an infinite focus state in an intermediate focal length state. FIG. 4C is a diagram illustrating various aberrations in the infinitely focused state in the telephoto end state. FIG. 6 is a cross-sectional view and a zoom locus illustrating a configuration of a zoom lens according to Example 2, where (W) is an infinitely focused state in a wide-angle end state, and (M) is an infinitely focused state in an intermediate focal length state. (T) indicates the infinite focus state in the telephoto end state. FIG. 6A is a diagram illustrating various aberrations of the zoom lens according to Example 2; FIG. 9A is a diagram illustrating various aberrations in an infinite focus state in a wide-angle end state, and FIG. 9B is an infinite focus state in an intermediate focal length state. FIG. 4C is a diagram illustrating various aberrations in the infinitely focused state in the telephoto end state. FIG. 8 is a cross-sectional view and a zoom locus illustrating a configuration of a zoom lens according to Example 3, where (W) is an infinite focus state in a wide-angle end state, and (M) is an infinite focus state in an intermediate focal length state. (T) indicates the infinite focus state in the telephoto end state. FIG. 6A is a diagram illustrating various aberrations of the zoom lens according to Example 3, wherein FIG. 9A is a diagram illustrating various aberrations in an infinite focus state in a wide-angle end state, and FIG. 9B is an infinite focus state in an intermediate focal length state. FIG. 4C is a diagram illustrating various aberrations in the infinitely focused state in the telephoto end state. FIG. 10 is a cross-sectional view and a zoom locus illustrating a configuration of a zoom lens according to Example 4, where (W) is an infinite focus state in a wide-angle end state, and (M) is an infinite focus state in an intermediate focal length state. (T) indicates the infinite focus state in the telephoto end state. FIG. 6A is a diagram illustrating various aberrations of the zoom lens according to Example 4, wherein FIG. 9A is a diagram illustrating various aberrations in an infinite focus state in a wide-angle end state, and FIG. 9B is an infinite focus state in an intermediate focal length state. FIG. 4C is a diagram illustrating various aberrations in the infinitely focused state in the telephoto end state. (A) is a front view of a digital still camera, (b) is a rear view of a digital still camera. FIG. 10 is a cross-sectional view taken along the line AA ′ in FIG. 5 is a flowchart for explaining a method of manufacturing a zoom lens according to the present embodiment.

  Hereinafter, the present embodiment will be described with reference to the drawings. As shown in FIG. 1, the zoom lens according to the present embodiment includes an optical element (a right-angle prism in the present embodiment) P for bending an optical path, and is arranged in order from the object side along the optical axis. A first lens group G1 having a refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, When it has a fifth lens group G5 having negative refractive power, the focal length of the first lens group G1 is fG1, and the focal length in the wide-angle end state of the zoom lens is fW, the following conditional expression (1) is satisfied: Satisfied.

  3.5 <fG1 / fW <10.0 (1)

  With this configuration, the magnification of the image formed by the first lens group G1 is changed by changing the distance between the first lens group G1 having a positive refractive power and the second lens G2 having a negative refractive power. It becomes possible. Further, by disposing the third lens group G3 having a positive refractive power on the image plane side of the second lens group G2, it is possible to prevent the light rays from diverging at the time of zooming. Further, by disposing a fourth lens group G4 having a positive refractive power on the image plane side of the third lens group G3, an image is formed by the fourth lens group G4, and an image plane movement due to zooming is corrected. Is possible. Furthermore, by disposing the fifth lens group G5 having negative refractive power on the image plane I side, the imaging position of the fourth lens G4 can be brought closer to the object side, and the total length of the optical system can be reduced. Become.

  Conditional expression (1) defines an appropriate ratio between the focal length fW of the zoom lens at the wide-angle end state and the focal length fG1 of the first lens group G1. Exceeding the upper limit of conditional expression (1) is not preferable because the focal length of the first lens group G1 becomes long and the entire optical system becomes large. Further, it is difficult to correct the fluctuation of astigmatism during zooming, which is not preferable. If the lower limit of conditional expression (1) is not reached, the focal length of the zoom lens at the wide-angle end state becomes long, and the image height must be increased to obtain the required angle of view. The whole becomes large and is not preferable. Further, it is difficult to correct the fluctuation of astigmatism during zooming, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 7.0. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 4.6.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 3.6. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 3.7.

  In the present embodiment, the first lens group G1 and the third lens group G3 are preferably fixed during zooming from the wide-angle end state to the telephoto end state.

  Thus, it is necessary to operate the largest lens group in the zoom lens by fixing the first lens group G1 located closest to the object side during zooming and focusing from the wide-angle end state to the telephoto end state. It can be made structurally simple. Further, by fixing the third lens group G3 arranged to prevent the light rays from the second lens group G2 from diverging, an increase in the luminous flux is prevented, and each lens group arranged on the image plane side is prevented. The diameter can be reduced.

  In the present embodiment, it is preferable that the aperture stop S for determining the luminous flux is disposed between the second lens group G2 and the third lens group G3.

  With this configuration, it is possible to reduce the height of light rays passing through the first lens group G1 in the wide-angle end state, and it is possible to reduce the height of light rays passing through the fourth lens group G4 in the telephoto end state. Therefore, it is possible to reduce the size of the entire optical system.

  In the present embodiment, the first lens group G1 includes a lens having negative refractive power (lens L11 in FIG. 1) arranged in order from the object side along the optical axis, and an optical element P for bending the optical path. And a lens having a positive refractive power (lens L12 in FIG. 1).

  With this configuration, the height of the light incident on the optical element P for bending the optical path can be kept low, so that the size of the optical element P can be reduced. Further, it is possible to satisfactorily correct the coma aberration in the wide-angle end state.

  In the present embodiment, the second lens group G2 includes a lens having a negative refractive power (lens L21 in FIG. 1) and a lens having a negative refractive power (in FIG. 1) arranged in order from the object side along the optical axis. It is preferable to have a lens L22) in FIG. 1 and a lens having a positive refractive power (lens L23 in FIG. 1).

  With this configuration, it is possible to satisfactorily correct variations in field curvature due to zooming. In addition, since the thickness of the entire second lens group G2 in the optical axis direction can be reduced, a large amount of movement associated with zooming of the second lens group G2 can be ensured. As a result, it is not necessary to increase the refractive power of the second lens group G2 more than necessary, and the aberration generated in the second lens group G2 can be reduced.

  In the present embodiment, it is preferable that at least one of the fourth lens group G4 and the fifth lens group G5 is composed only of a cemented lens (in FIG. 1, the fourth lens group G4 and the fifth lens group G5). Both are applicable).

  With this configuration, fluctuations in coma due to zooming can be corrected well.

  In the present embodiment, at least one of the fourth lens group G4 and the fifth lens group G5 is composed of only a cemented lens of a lens having a positive refractive power and a lens having a negative refractive power. Is preferable (in FIG. 1, both the fourth lens group G4 and the fifth lens group G5 are applicable).

  With this configuration, fluctuations in coma due to zooming can be corrected well.

  9 and 10 show a digital still camera 1 (optical apparatus) including the zoom lens as the photographing lens ZL. In the digital still camera 1, when a power button (not shown) is pressed, a shutter (not shown) of the photographing lens ZL is opened, and light from a subject (object) is condensed by the photographing lens ZL and arranged on the image plane I. The image is formed on an image sensor C (for example, composed of a CCD, a CMOS, or the like). The subject image formed on the image sensor C is displayed on the liquid crystal monitor 2 disposed behind the digital still camera 1. The photographer determines the composition of the subject image while looking at the liquid crystal monitor 2, and then depresses the release button 3 to photograph the subject image with the image sensor C, and records and saves it in a memory (not shown).

  The camera 1 includes an auxiliary light emitting unit 4 that emits auxiliary light when the subject is dark, and a wide (W) when zooming the photographing lens ZL from the wide-angle end state (W) to the telephoto end state (T). -A tele (T) button 5 and function buttons 6 used for setting various conditions of the digital still camera 1 are arranged.

  Next, a method for manufacturing the zoom lens having the above configuration will be described with reference to FIG. First, each lens (the lenses L11 to L52 and the optical element P for bending the optical path in FIG. 1) is incorporated in the lens barrel (step S1). When assembling each lens in the lens barrel, the lenses may be incorporated in the lens barrel one by one in the order along the optical axis, and a part or all of the lenses are integrally held by the holding member and then assembled with the lens barrel member. Also good. Next, after each lens is incorporated in the lens barrel, it is confirmed whether an object image is formed in a state where each lens is incorporated in the lens barrel, that is, whether the centers of the lenses are aligned (step) S2). Subsequently, various operations of the zoom lens are confirmed (step S3). Examples of various operations include a zooming operation that zooms from the wide-angle end state to the telephoto end state, and a focusing operation that moves the lens that focuses from a long-distance object to a short-distance object along the optical axis direction. Etc. Note that the order of confirming the various operations is arbitrary.

  Hereinafter, each example according to the present embodiment will be described with reference to the drawings. Tables 1 to 4 are shown below, but these are tables of specifications in the first to fourth examples. In [Overall specifications], f is the focal length of the zoom lens, FNo is the F number, ω is the half field angle, Y is the image height, TL is the total lens length, and Bf is the back focus. In [Lens data], the surface number is the order of the lens surfaces from the object side along the direction in which the light beam travels, r is the radius of curvature of each lens surface, and d is the next optical surface from each optical surface (or The distance between the surfaces, which is the distance on the optical axis to the image plane), nd is the refractive index for the d-line (wavelength 587.6 nm), and νd is the Abbe number for the d-line. When the lens surface is aspherical, an asterisk is attached to the surface number, and the paraxial radius of curvature is indicated in the column of the radius of curvature r. The curvature radius “∞” indicates a plane or an opening. In [ZOOMING DATA], di (where i is an integer) indicates a variable interval between the i-th surface and the (i + 1) -th surface in each state of the wide-angle end state, the intermediate focal length state, and the telephoto end state. In [Zoom Lens Group Data], the initial surface and focal length of each group are shown. In [Conditional Expression], a value corresponding to the conditional expression (1) is shown.

In [Aspherical data], the shape of the aspherical surface shown in [Lens data] is shown by the following equation (a). That is, y is the height in the direction perpendicular to the optical axis, and S (y) is the distance (sag amount) along the optical axis from the tangent plane at the apex of the aspheric surface to the position on the aspheric surface at height y. When the radius of curvature of the reference spherical surface (paraxial radius of curvature) is r, the conic coefficient is κ, and the n-th aspherical coefficient is An, the following equation (a) is given. In each example, the secondary aspheric coefficient A2 is 0, and the description thereof is omitted. E-n represents ^x10 -n. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ .

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 ... (a)

  In the table, “mm” is generally used as the focal length f, radius of curvature r, surface interval d, and other length units. However, since the optical system can obtain the same optical performance even when proportionally enlarged or proportionally reduced, the unit is not limited to “mm”, and other appropriate units can be used.

  The description of the above table is the same in other examples, and the description thereof is omitted.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. FIG. 1 shows the configuration of the zoom lens according to the first embodiment, and changes in the focal length state from the wide-angle end state (W) through the intermediate focal length state (M) to the telephoto end state (T), that is, zooming. The state of movement of each lens group at the time is shown. In the zoom lens according to the first example, the optical path is polarized by 90 degrees by a right-angle prism P (an optical element for bending the optical path) as shown in FIG. ing.

  The zoom lens according to the first example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and a positive lens. It has a third lens group G3 having a refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power.

  The first lens group G1 includes a negative meniscus lens L11 arranged in order from the object side along the optical axis and having a convex surface directed toward the object side, a right-angle prism P for bending the optical path by 90 degrees, and a biconvex positive lens. L12.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a biconcave negative lens L22, and a positive meniscus lens having a convex surface directed toward the object side, which are arranged in order from the object side along the optical axis. And a cemented lens with L23.

  The third lens group G3 includes a biconvex positive lens L31, and a cemented lens of a biconvex positive lens L32 and a biconcave negative lens L33, which are arranged in order from the object side along the optical axis. .

  The fourth lens group G4 includes a cemented lens of a biconvex positive lens L41 and a negative meniscus lens L42 having a convex surface directed toward the image plane, which are arranged in order from the object side along the optical axis.

  The fifth lens group G5 has a cemented lens of a biconvex positive lens L51 and a biconcave negative lens L52 arranged in order from the object side along the optical axis.

  In addition, an aperture stop S for determining a light beam is disposed between the second lens group G2 and the third lens group G3.

  Further, a low-pass filter LPF for cutting a spatial frequency equal to or higher than the limit resolution of the solid-state imaging device is disposed between the fifth lens group G5 and the image plane I. The image plane I is formed on the image sensor C shown in FIG. 10, and the image sensor C is composed of a CCD, a CMOS, or the like.

  In the zoom lens of the present embodiment having the above-described configuration, the first lens group G1, the aperture stop S, and the third lens group G3 are fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state. The second lens group G2, the fourth lens group G4, and the fifth lens group G5 are moved.

  Table 1 below shows a table of specifications in the first embodiment. In addition, the surface numbers 1-27 in Table 1 respond | correspond to the surfaces 1-27 shown in FIG. In the first embodiment, the fifth surface, the sixth surface, the eighth surface, the fourteenth surface, and the eighteenth surface are all formed in an aspherical shape.

(Table 1)
[Lens data]
Surface number r d nd νd
Object ∞
1 28.03251 0.70000 1.922860 20.88
2 8.75609 2.70000 1.000000
3 ∞ 8.40000 1.846660 23.78
4 ∞ 0.20000 1.000000
* 5 14.01544 2.55000 1.693500 53.22
* 6 -20.45263 d6 1.000000
7 226.20746 0.70000 1.765460 46.73
* 8 6.60497 1.04048 1.000000
9 -19.49009 0.50000 1.882997 40.76
10 6.40312 1.70000 1.922860 20.88
11 450.76250 d11 1.000000
12 ∞ 0.30000 1.000000 (Aperture stop)
13 12.49208 1.30000 1.688630 53.22
* 14 -16.96606 0.10000 1.000000
15 8.77832 1.70000 1.518230 58.93
16 -7.14560 0.40000 1.882997 40.76
17 16.21897 d17 1.000000
* 18 15.09088 3.45000 1.693500 53.22
19 -5.50000 0.65000 1.903660 31.31
20 -11.63949 d20 1.000000
21 7.84668 2.95000 1.603001 65.44
22 -7.05000 0.50000 1.834000 37.16
23 7.17217 d23 1.000000
24 ∞ 0.21000 1.516330 64.14
25 ∞ 1.00000 1.000000
26 ∞ 0.50000 1.516330 64.14
27 ∞ Bf 1.000000
Image plane ∞
[Aspherical data]
5th surface κ = 1.0000, A4 = -1.03690E-04, A6 = -7.08780E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = 1.0000, A4 = -4.56890E-05, A6 = -2.45090E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
8th surface κ = 1.0000, A4 = -2.01720E-04, A6 = 1.25860E-05, A8 = 0.00000E + 00, A10 = 0.00000E + 00
14th surface κ = 1.0000, A4 = -1.70450E-04, A6 = -4.90640E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
18th surface κ = 9.0017, A4 = -3.92170E-04, A6 = 4.26910E-06, A8 = -5.06540E-07, A10 = 0.00000E + 00
[Overall specifications]
Zoom ratio 3.7609
Wide angle end Intermediate focal length Telephoto end f 4.60000 6.89092 17.30000
FNo 3.82128 3.94775 5.36201
ω 43.37043 30.62070 13.03350
Y 4.05000 4.05000 4.05000
TL 55.00010 54.99984 54.99993
Bf 0.60009 0.59990 0.59995
[Zooming data]
Variable interval Wide angle end Intermediate focal length Telephoto end d6 0.50000 4.01443 8.74812
d11 8.84815 5.33372 0.60000
d17 9.13203 7.06071 1.69976
d20 1.00000 2.25815 4.55933
d23 3.36934 4.18245 7.24228
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 18.11272
G2 7 -6.31582
G3 13 14.50694
G4 18 12.28649
G5 21 -20.17049
[Conditional expression]
Conditional expression (1) fG1 / fW = 3.9375

  From the table of specifications shown in Table 1, it can be seen that the zoom lens according to the present example satisfies the conditional expression (1).

  2A and 2B are graphs showing various aberrations of the zoom lens according to Example 1. FIG. 2A is a diagram showing various aberrations in the infinite focus state at the wide-angle end state, and FIG. 2B is infinity in the intermediate focal length state. FIG. 5C is a diagram illustrating various aberrations in a far-focus state, and FIG. 9C is a diagram illustrating various aberrations in an infinite focus state in the telephoto end state.

  In each aberration diagram, FNO indicates an F number, and Y indicates an image height. In the spherical aberration diagram, a solid line indicates spherical aberration, and a broken line indicates a sine condition (sine condition). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. Further, in coma aberration, the solid line indicates meridional coma. The explanation of the above aberration diagrams is the same in the other examples, and the explanation is omitted.

  As is apparent from the respective aberration diagrams, in the first example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Second embodiment)
A second embodiment will be described with reference to FIGS. 3 and 4 and Table 2. FIG. FIG. 3 shows the configuration of the zoom lens according to Example 2, and the change in the focal length state from the wide-angle end state (W) through the intermediate focal length state (M) to the telephoto end state (T), that is, zooming. The state of movement of each lens group at the time is shown. In the zoom lens according to the second embodiment, the optical path is polarized by 90 degrees by a right-angle prism P (an optical element for bending the optical path) as shown in FIG. ing.

  The zoom lens according to the second example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and a positive lens. It has a third lens group G3 having a refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power.

  The first lens group G1 includes a negative meniscus lens L11 arranged in order from the object side along the optical axis and having a convex surface directed toward the object side, a right-angle prism P for bending the optical path by 90 degrees, and a biconvex positive lens. L12.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a biconcave negative lens L22, and a positive meniscus lens having a convex surface directed toward the object side, which are arranged in order from the object side along the optical axis. And a cemented lens with L23.

  The third lens group G3 includes a biconvex positive lens L31, and a cemented lens of a biconvex positive lens L32 and a biconcave negative lens L33, which are arranged in order from the object side along the optical axis. .

  The fourth lens group G4 includes a cemented lens of a biconvex positive lens L41 and a negative meniscus lens L42 having a convex surface directed toward the image plane, which are arranged in order from the object side along the optical axis.

  The fifth lens group G5 has a cemented lens of a biconvex positive lens L51 and a biconcave negative lens L52 arranged in this order from the object side along the optical axis.

  In addition, an aperture stop S for determining a light beam is disposed between the second lens group G2 and the third lens group G3.

  Further, a low-pass filter LPF for cutting a spatial frequency equal to or higher than the limit resolution of the solid-state imaging device is disposed between the fifth lens group G5 and the image plane I. The image plane I is formed on the image sensor C shown in FIG. 10, and the image sensor C is composed of a CCD, a CMOS, or the like.

  In the zoom lens of the present embodiment having the above-described configuration, the first lens group G1, the aperture stop S, and the third lens group G3 are fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state. The second lens group G2, the fourth lens group G4, and the fifth lens group G5 are moved.

  Table 2 shows a table of specifications in the second embodiment. In addition, the surface numbers 1-27 in Table 2 respond | correspond to the surfaces 1-27 shown in FIG. In the second embodiment, the fifth surface, the sixth surface, the eighth surface, the fourteenth surface, and the eighteenth surface are all aspherical.

(Table 2)
[Lens data]
Surface number r d nd νd
Object ∞
1 28.31515 0.70000 1.922860 20.88
2 8.74961 2.70000 1.000000
3 ∞ 8.40000 1.846660 23.78
4 ∞ 0.20000 1.000000
* 5 13.88901 2.55000 1.693500 53.22
* 6 -20.25199 d6 1.000000
7 117.91390 0.70000 1.765460 46.73
* 8 6.49803 1.07281 1.000000
9 -17.98106 0.50000 1.882997 40.76
10 6.44025 1.70000 1.922860 20.88
11 2225.80710 d11 1.000000
12 ∞ 0.30000 1.000000 (Aperture stop)
13 12.62907 1.30000 1.688630 53.22
* 14 -16.96992 0.10000 1.000000
15 8.78742 1.70000 1.518230 58.93
16 -7.12567 0.40000 1.882997 40.76
17 16.52123 d17 1.000000
* 18 15.19240 3.45000 1.693500 53.22
19 -5.50000 0.65000 1.903660 31.31
20 -11.63884 d20 1.000000
21 7.90816 2.95000 1.603001 65.44
22 -7.05000 0.50000 1.834000 37.16
23 7.27747 d22 1.000000
24 ∞ 0.21000 1.516330 64.14
25 ∞ 1.00000 1.000000
26 ∞ 0.50000 1.516330 64.14
27 ∞ Bf 1.000000
Image plane ∞
[Aspherical data]
5th surface κ = 1.0000, A4 = -1.05350E-04, A6 = -7.28660E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = 1.0000, A4 = -4.38050E-05, A6 = -2.47110E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
8th surface κ = 1.0000, A4 = -1.90780E-04, A6 = 1.37050E-05, A8 = 0.00000E + 00, A10 = 0.00000E + 00
14th surface κ = 1.0000, A4 = -1.74990E-04, A6 = -4.93710E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
18th surface κ = 9.0834, A4 = -3.87050E-04, A6 = 4.07510E-06, A8 = -4.88730E-07, A10 = 0.00000E + 00
[Overall specifications]
Zoom ratio 3.7609
Wide angle end Intermediate focal length Telephoto end f 4.60000 7.00000 17.30001
FNo 3.82550 3.96908 5.32530
ω 43.37035 30.22723 13.04558
Y 4.05000 4.05000 4.05000
TL 55.00005 54.99987 54.99994
Bf 0.60004 0.59991 0.59998
[Zooming data]
Variable interval Wide angle end Intermediate focal length Telephoto end d6 0.50000 4.07957 8.73225
d11 8.83229 5.25272 0.60000
d17 9.05596 6.93230 1.75897
d20 1.00000 2.24147 4.44643
d23 3.42895 4.31109 7.27950
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 17.78287
G2 7 -6.28186
G3 13 14.52979
G4 18 12.32734
G5 21 -20.43552
[Conditional expression]
Conditional expression (1) fG1 / fW = 3.8658

  From the table of specifications shown in Table 2, it can be seen that the zoom lens according to the present example satisfies the conditional expression (1).

  4A and 4B are graphs showing various aberrations of the zoom lens according to Example 2. FIG. 4A is a diagram showing various aberrations in the infinitely focused state at the wide-angle end state, and FIG. 4B is infinity in the intermediate focal length state. FIG. 5C is a diagram illustrating various aberrations in a far-focus state, and FIG. 9C is a diagram illustrating various aberrations in an infinite focus state in the telephoto end state.

  As is apparent from the respective aberration diagrams, in the second example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Third embodiment)
A third embodiment will be described with reference to FIGS. FIG. 5 shows the configuration of the zoom lens according to Example 3, and the change in the focal length state from the wide-angle end state (W) through the intermediate focal length state (M) to the telephoto end state (T), that is, zooming. The state of movement of each lens group at the time is shown. In the zoom lens according to the third example, the optical path is polarized by 90 degrees by a right-angle prism P (an optical element for bending the optical path) as shown in FIG. ing.

  The zoom lens according to the third example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and a positive lens. It has a third lens group G3 having a refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power.

  The first lens group G1 includes a negative meniscus lens L11 arranged in order from the object side along the optical axis and having a convex surface directed toward the object side, a right-angle prism P for bending the optical path by 90 degrees, and a biconvex positive lens. L12.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a biconcave negative lens L22, and a positive meniscus lens having a convex surface directed toward the object side, which are arranged in order from the object side along the optical axis. And a cemented lens with L23.

  The third lens group G3 includes a biconvex positive lens L31, and a cemented lens of a biconvex positive lens L32 and a biconcave negative lens L33, which are arranged in order from the object side along the optical axis. .

  The fourth lens group G4 includes a cemented lens of a biconvex positive lens L41 and a negative meniscus lens L42 having a convex surface directed toward the image plane, which are arranged in order from the object side along the optical axis.

  The fifth lens group G5 has a cemented lens of a biconvex positive lens L51 and a biconcave negative lens L52 arranged in this order from the object side along the optical axis.

  In addition, an aperture stop S for determining a light beam is disposed between the second lens group G2 and the third lens group G3.

  Further, a low-pass filter LPF for cutting a spatial frequency equal to or higher than the limit resolution of the solid-state imaging device is disposed between the fifth lens group G5 and the image plane I. The image plane I is formed on the image sensor C shown in FIG. 10, and the image sensor C is composed of a CCD, a CMOS, or the like.

  In the zoom lens of the present embodiment having the above-described configuration, the first lens group G1, the aperture stop S, and the third lens group G3 are fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state. The second lens group G2, the fourth lens group G4, and the fifth lens group G5 are moved.

  Table 3 shows a table of specifications in the third embodiment. The surface numbers 1 to 27 in Table 3 correspond to the surfaces 1 to 27 shown in FIG. In the third embodiment, the fifth surface, the sixth surface, the eighth surface, the fourteenth surface, and the eighteenth surface are all formed in an aspherical shape.

(Table 3)
[Lens data]
Surface number r d nd νd
Object ∞
1 27.99361 0.70000 1.922860 20.88
2 8.75601 2.70000 1.000000
3 ∞ 8.40000 1.846660 23.78
4 ∞ 0.20000 1.000000
* 5 14.07687 2.55000 1.693500 53.22
* 6 -20.34407 d6 1.000000
7 238.09082 0.70000 1.765460 46.73
* 8 6.63847 1.03865 1.000000
9 -19.33036 0.50000 1.882997 40.76
10 6.39728 1.70000 1.922860 20.88
11 443.77077 d11 1.000000
12 ∞ 0.30000 1.000000 (Aperture stop)
13 12.54866 1.30000 1.688630 53.22
* 14 -16.86341 0.10000 1.000000
15 8.76469 1.70000 1.518230 58.93
16 -7.15051 0.40000 1.882997 40.76
17 16.18726 d17 1.000000
* 18 15.15775 3.45000 1.693500 53.22
19 -5.50000 0.65000 1.903660 31.31
20 -11.61180 d20 1.000000
21 7.81731 2.95000 1.603001 65.44
22 -7.05000 0.50000 1.834000 37.16
23 7.14096 d23 1.000000
24 ∞ 0.21000 1.516330 64.14
25 ∞ 1.00000 1.000000
26 ∞ 0.50000 1.516330 64.14
27 ∞ Bf 1.000000
Image plane ∞
[Aspherical data]
5th surface κ = 1.0000, A4 = -1.02930E-04, A6 = -6.97990E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = 1.0000, A4 = -4.50000E-05, A6 = -2.45690E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
8th surface κ = 1.0000, A4 = -1.97150E-04, A6 = 1.30290E-05, A8 = 0.00000E + 00, A10 = 0.00000E + 00
14th surface κ = 1.0000, A4 = -1.70170E-04, A6 = -4.84040E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
18th surface κ = 9.0961, A4 = -3.91200E-04, A6 = 4.36630E-06, A8 = -5.11360E-07, A10 = 0.00000E + 00
[Overall specifications]
Zoom ratio 3.7609
Wide angle end Intermediate focal length Telephoto end f 4.60000 6.88467 17.30000
FNo 3.82030 3.94841 5.36408
ω 43.37080 30.61556 13.02593
Y 4.05000 4.05000 4.05000
TL 55.00011 54.99984 54.99992
Bf 0.60011 0.59990 0.59996
[Zooming data]
Variable interval Wide-angle end Intermediate focal length Telephoto end d6 0.50000 4.00282 8.74397
d11 8.84400 5.34118 0.60000
d17 9.14049 7.07035 1.69750
d20 1.00000 2.24367 4.56528
d23 3.36686 4.19327 7.24456
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 18.12013
G2 7 -6.31494
G3 13 14.49997
G4 18 12.28853
G5 21 -20.14947
[Conditional expression]
Conditional expression (1) fG1 / fW = 3.9392

  From the table of specifications shown in Table 3, it can be seen that the zoom lens according to the present example satisfies the conditional expression (1).

  6A and 6B are graphs showing various aberrations of the zoom lens according to Example 3. FIG. 6A is a diagram showing various aberrations in the infinite focus state at the wide-angle end state, and FIG. 6B is infinity in the intermediate focal length state. FIG. 5C is a diagram illustrating various aberrations in a far-focus state, and FIG. 9C is a diagram illustrating various aberrations in an infinite focus state in the telephoto end state.

  As is apparent from the respective aberration diagrams, in the third example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Fourth embodiment)
A fourth embodiment will be described with reference to FIGS. FIG. 7 shows the configuration of the zoom lens according to Example 4, and the change in the focal length state from the wide-angle end state (W) through the intermediate focal length state (M) to the telephoto end state (T), that is, zooming. The state of movement of each lens group at the time is shown. In the zoom lens according to the fourth example, the optical path is polarized by 90 degrees by a right-angle prism P (an optical element for bending the optical path) as shown in FIG. ing.

  The zoom lens according to Example 4 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, arranged in order from the object side along the optical axis, and a positive lens. It has a third lens group G3 having a refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power.

  The first lens group G1 includes a negative meniscus lens L11 arranged in order from the object side along the optical axis and having a convex surface directed toward the object side, a right-angle prism P for bending the optical path by 90 degrees, and a biconvex positive lens. L12.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a biconcave negative lens L22, and a positive meniscus lens having a convex surface directed toward the object side, which are arranged in order from the object side along the optical axis. And a cemented lens with L23.

  The third lens group G3 includes a biconvex positive lens L31, and a cemented lens of a biconvex positive lens L32 and a biconcave negative lens L33, which are arranged in order from the object side along the optical axis. .

  The fourth lens group G4 includes a cemented lens of a biconvex positive lens L41 and a negative meniscus lens L42 having a convex surface directed toward the image plane, which are arranged in order from the object side along the optical axis.

  The fifth lens group G5 has a cemented lens of a biconvex positive lens L51 and a biconcave negative lens L52 arranged in order from the object side along the optical axis.

  In addition, an aperture stop S for determining a light beam is disposed between the second lens group G2 and the third lens group G3.

  Further, a low-pass filter LPF for cutting a spatial frequency equal to or higher than the limit resolution of the solid-state imaging device is disposed between the fifth lens group G5 and the image plane I. The image plane I is formed on the image sensor C shown in FIG. 10, and the image sensor C is composed of a CCD, a CMOS, or the like.

  In the zoom lens of the present embodiment having the above-described configuration, the first lens group G1, the aperture stop S, and the third lens group G3 are fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state. The second lens group G2, the fourth lens group G4, and the fifth lens group G5 are moved.

  Table 4 shows a table of specifications in the fourth embodiment. In addition, the surface numbers 1-27 in Table 4 respond | correspond to the surfaces 1-27 shown in FIG. In the fourth embodiment, the fifth surface, the sixth surface, the eighth surface, the fourteenth surface, and the eighteenth surface are all formed in an aspherical shape.

(Table 4)
[Lens data]
Surface number r d nd νd
Object ∞
1 27.86919 0.70000 1.922860 20.88
2 8.72269 2.70000 1.000000
3 ∞ 8.40000 1.846660 23.78
4 ∞ 0.20000 1.000000
* 5 14.05390 2.55000 1.693500 53.22
* 6 -20.29324 d6 1.000000
7 315.50692 0.70000 1.765460 46.73
* 8 6.64117 1.05836 1.000000
9 -19.80866 0.50000 1.882997 40.76
10 6.39742 1.70000 1.922860 20.88
11 390.54014 d11 1.000000
12 0.00000 0.30000 1.000000 (Aperture stop)
13 12.48966 1.30000 1.688630 53.22
* 14 -16.93792 0.10000 1.000000
15 8.76925 1.70000 1.518230 58.93
16 -7.14295 0.40000 1.882997 40.76
17 16.18847 d17 1.000000
* 18 15.12489 3.45000 1.693500 53.22
19 -5.50000 0.65000 1.903660 31.31
20 -11.64496 d20 1.000000
21 7.80458 2.95000 1.603001 65.44
22 -7.05000 0.50000 1.834000 37.16
23 7.12554 d23 1.000000
24 ∞ 0.21000 1.516330 64.14
25 ∞ 1.00000 1.000000
26 ∞ 0.50000 1.516330 64.14
27 ∞ Bf 1.000000
Image plane ∞
[Aspherical data]
5th surface κ = 1.0000, A4 = -1.03640E-04, A6 = -7.02250E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
6th surface κ = 1.0000, A4 = -4.54720E-05, A6 = -2.46610E-07, A8 = 0.00000E + 00, A10 = 0.00000E + 00
8th surface κ = 1.0000, A4 = -2.03080E-04, A6 = 1.24790E-05,8 = 0.00000E + 00, A10 = 0.00000E + 00
14th surface κ = 1.0000, A4 = -1.70540E-04, A6 = -4.86450E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
18th surface κ = 8.9044, A4 = -3.84020E-04, A6 = 4.18780E-06, A8 = -4.76180E-07, A10 = 0.00000E + 00
[Overall specifications]
Zoom ratio 3.7609
Wide angle end Intermediate focal length Telephoto end f 4.60000 6.86278 17.30000
FNo 3.82536 3.95193 5.37769
ω 43.37029 30.71049 13.02950
Y 4.05000 4.05000 4.05000
TL 55.00011 54.99984 54.99993
Bf 0.60011 0.59989 0.59996
[Zooming data]
Variable interval Wide angle end Intermediate focal length Telephoto end d6 0.50000 3.97618 8.73001
d11 8.83004 5.35386 0.60000
d17 9.13424 7.08055 1.68926
d20 1.00000 2.23953 4.52905
d23 3.36736 4.18147 7.28329
[Zoom lens group data]
Group number Group first surface Group focal length G1 1 18.06900
G2 7 -6.31290
G3 13 14.49469
G4 18 12.30539
G5 21 -20.12971
[Conditional expression]
Conditional expression (1) fG1 / fW = 3.92804

  From the table of specifications shown in Table 4, it can be seen that the zoom lens according to the present example satisfies the conditional expression (1).

  FIGS. 8A and 8B are graphs showing various aberrations of the zoom lens according to Example 4. FIG. 8A is a graph showing various aberrations in the infinite focus state at the wide-angle end state, and FIG. 8B is infinity in the intermediate focal length state. FIG. 5C is a diagram illustrating various aberrations in a far-focus state, and FIG. 9C is a diagram illustrating various aberrations in an infinite focus state in the telephoto end state.

  As is apparent from each aberration diagram, in the fourth example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

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

  In each embodiment, a five-group configuration is shown as a zoom lens, but the present invention can also be applied to other group configurations such as a sixth group and a seventh group. 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 refers to a portion having at least one lens separated by an air interval that changes during zooming.

  Further, in the present embodiment, 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 fourth lens group G4 or the fifth lens group G5 is preferably a focusing lens group.

  In this embodiment, the lens group or the partial lens group is vibrated in a direction perpendicular to the optical axis, or rotated (oscillated) in an in-plane direction including the optical axis to correct image blur caused by camera shake. An anti-vibration lens group may be used. In particular, it is preferable that at least a part of the third lens group G3 is an anti-vibration lens group.

  In the present embodiment, 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. If the lens surface is aspherical, the aspherical surface is an aspherical surface by grinding, a glass mold aspherical surface that is formed of glass with an aspherical shape, or a composite type nonspherical surface that is formed of a resin on the surface of glass. Any aspherical surface may be used. In the present embodiment, it is preferable to use three or more aspheric surfaces. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In the present embodiment, the aperture stop S is preferably disposed in the vicinity of the third lens group G3. However, the role of the aperture stop may be substituted by a lens frame without providing a member as the aperture stop.

  In this embodiment, 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 (variable magnification optical system) of the present embodiment has a magnification ratio of about 4.0.

  In the zoom lens (variable magnification optical system) of the present embodiment, it is preferable that the first lens group G1 has at least one positive lens component and one negative lens component. The first lens group G1 includes negative lenses, prisms, positive lenses arranged in order from the object side, or negative lenses, prisms, positive lenses, and positive lenses arranged in order from the object side, with an air gap interposed therebetween. It is preferable to do this.

  In the present embodiment, the second lens group G2 may include a negative lens on the front side (object side) and a positive lens or a negative lens on the rear side (image side).

  In the present embodiment, the fourth lens group G4 may add a positive lens to the front side (object side).

  In addition, in order to make this invention intelligible, although demonstrated with the component requirement of embodiment, it cannot be overemphasized that this invention is not limited to this.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group P Right angle prism (optical element for bending optical path)
S aperture stop I image plane LPF low-pass filter 1 digital still camera (optical equipment)
ZL photography lens (zoom lens)

Claims (9)

In a zoom lens having an optical element for bending an optical path,
A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, arranged in order from the object side along the optical axis; A fourth lens group having refractive power and a fifth lens group having negative refractive power;
When the focal length of the first lens group is fG1, and the focal length of the zoom lens in the wide-angle end state is fW, the following expression 3.5 <fG1 / fW <10.0
A zoom lens that satisfies the following conditions.   2. The zoom lens according to claim 1, wherein the first lens group and the third lens group are fixed during zooming from the wide-angle end state to the telephoto end state.   3. The zoom lens according to claim 1, wherein an aperture stop for determining a light beam is disposed between the second lens group and the third lens group.   The first lens group includes a lens having negative refractive power, arranged in order from the object side along the optical axis, an optical element for bending the optical path, and a lens having positive refractive power. The zoom lens according to claim 1, wherein the zoom lens is a zoom lens.   The second lens group includes a lens having a negative refractive power, a lens having a negative refractive power, and a lens having a positive refractive power, which are arranged in order from the object side along the optical axis. The zoom lens according to any one of claims 1 to 4.   6. The zoom lens according to claim 1, wherein at least one of the fourth lens group and the fifth lens group includes only a cemented lens.   2. At least one of the fourth lens group and the fifth lens group is composed of only a cemented lens of a lens having a positive refractive power and a lens having a negative refractive power. The zoom lens as described in any one of -6.   An optical apparatus comprising the zoom lens according to any one of claims 1 to 7. A method for manufacturing a zoom lens having an optical element for bending an optical path,
A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, arranged in order from the object side along the optical axis; A fourth lens group having refractive power and a fifth lens group having negative refractive power;
When the focal length of the first lens group is fG1, and the focal length of the zoom lens in the wide-angle end state is fW, the following expression 3.5 <fG1 / fW <10.0
A method for manufacturing a zoom lens, comprising: mounting each lens in a lens barrel so as to satisfy the above conditions, and performing an operation check.

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