JP5305889B2 - Zoom lens and imaging apparatus having the same - Google Patents

Description

  The present invention relates to a zoom lens, and is particularly suitable for a silver salt film camera, an electronic recording digital camera, a video camera, and the like.

  Conventionally, as a zoom lens for a single lens reflex camera, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third group having a negative refractive power, and a positive lens A zoom lens in which a fourth lens unit having a refractive power is arranged is known. This type of zoom lens is a so-called negative lead type preceded by a lens group having a negative refractive power, and is therefore suitable for widening the angle of view. At the telephoto end, the first lens group and the second lens group constitute a positive refractive power group as a whole, and the third lens group and the fourth lens group constitute a negative refractive power group as a whole. Since it can be of a so-called telephoto type, there is an advantage that a long focal length is easily obtained at the telephoto end.

As described above, since the configuration is advantageous for widening the angle and increasing the focal length of the optical system, it has been adopted as a lens configuration of a standard zoom lens, and various zoom lenses have been proposed. (Patent Documents 1 and 2)
Japanese Unexamined Patent Publication No. 2000-33897 JP 2004-212541 A

  In recent years, a standard zoom lens used in a photographing apparatus is strongly required to have a high zoom ratio, a wide angle of view, and a high image quality of a photographed image.

  In particular, in a zoom lens used in a single-lens reflex camera, it is necessary to consider that a long back focus is required in order to arrange a quick return mirror and a low-pass filter in order to widen a shooting angle of view. For this purpose, the refractive power of the lens group constituting the zoom lens must be appropriate.

  A zoom lens including a lens group having negative, positive, negative, and positive refractive power in order from the object side to the image side has a negative lead type lens configuration at the wide angle end. For this reason, the back focus can be ensured by increasing the refractive power of the lens group having a negative refractive power on the object side and the lens group having a positive refractive power on the image side. However, since the asymmetry of the refractive power arrangement before and after the stop increases, negative distortion is greatly generated. Further, when the telephoto end of the zoom lens is made to have a long focal length, the total lens length increases.

  At the telephoto end, the first lens group and the second lens group as a whole form a positive refractive power group, and the third lens group and the fourth lens group as a whole form a negative refractive power group. By doing so, the increase in the total lens length can be reduced. However, the asymmetry of the power arrangement before and after the stop increases, and a large amount of positive distortion occurs.

  In addition, since the first lens group and the fourth lens group have a relatively high incident height (distance from the optical axis) h of the paraxial ray of the pupil to the lens surface, the first lens group and the fourth lens group are aspherical. By using this, it is possible to reduce the amount of variation in distortion during zooming. In other words, an aspherical surface is inserted into two surfaces: a surface with a large amount of distortion at the wide-angle end relative to the telephoto end and a surface with a large amount of distortion at the telephoto end relative to the wide-angle end. By increasing it, the amount of variation in distortion can be reduced. However, if the amount of aspherical surface is too large to correct distortion, aberrations other than distortion, such as astigmatism, deteriorate, so that fluctuations in distortion cannot be corrected sufficiently.

  The present invention has been made in view of the above, and in a zoom lens having a lens group of negative, positive, negative, and positive refractive power in order from the object side to the image side, the amount of variation in distortion due to zooming is small. An object of the present invention is to provide a zoom lens having good optical performance.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive lens having a positive refractive power. is a fourth lens unit, the hand during zooming from the wide-angle end to the telephoto end, the interval between groups adjacent lens is changed, in the zoom lens of the first lens group distance between the second lens group becomes small, the The first lens group has a positive lens closest to the object side, the fourth lens group has a negative lens closest to the image side, the focal length of the first lens group is f1, and the second lens group at the wide-angle end. F24 is the combined focal length from the first lens group to the fourth lens group, fw is the focal length of the entire system at the wide-angle end, and the radius of curvature of the lens surface on the image side of the negative lens disposed closest to the image side of the fourth lens group is Rn , a negative lens disposed on the most image side of the fourth lens group When the radius of curvature of the lens surface on the object side of the lens is R1,
0.5 <| f1 / f24 | <1.4
0.50 <Rn / fw <15.0
−0.8 <(Rn + R1) / (Rn−R1) ≦ 0.18
It satisfies the following conditional expression.

  According to the present invention, it is possible to provide a zoom lens that has a small amount of variation in distortion during zooming and has good optical performance.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, a third lens unit L3 having a negative refractive power, and a positive lens unit. A fourth lens unit L4 having refractive power is included.

  During zooming, the distance between the first lens unit L1 and the second lens unit L2 is moved to be smaller at the telephoto end than at the wide-angle end.

  FIG. 1 is a lens cross-sectional view at the wide angle end (short focal length end) of the zoom lens of Embodiment 1, and FIG. 2 is a wide angle end, an intermediate focal length, and a telephoto end (long focal length end) of the zoom lens of Embodiment 1, respectively. FIG.

  FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens of Example 2, and FIG. 4 is an aberration diagram at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 2, respectively.

  FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens of Example 3, and FIG. 6 is an aberration diagram at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 3, respectively.

  FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens of Example 4, and FIG. 8 is an aberration diagram at the wide-angle end, intermediate focal length, and telephoto end of the zoom lens of Example 4, respectively.

  FIG. 9 is a schematic view of a main part of a camera (image pickup apparatus) including the zoom lens according to the present invention.

  The zoom lens of each embodiment is a photographing lens used in an imaging apparatus such as a digital camera or a video camera. In the lens cross-sectional view, the left side is the subject side (front), and the right side is the image side (rear).

  In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group. The arrows indicate the movement trajectory of each lens unit during zooming from the wide-angle end to the telephoto end.

  SP is an aperture stop (F-number determining stop). IP is an image plane, and when used as a photographing optical system of a video camera or a digital still camera, an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is placed.

  In the aberration diagrams, d and g are d-line and g-line, M and S are meridional image plane, sagittal image plane, S.P. C. Is a sine condition, and lateral chromatic aberration is represented by a g-line. ω is a half angle of view, and Fno is an F number.

  In each of the following embodiments, the wide-angle end and the telephoto end are zoom positions when the second lens unit L2 is positioned at both ends of the range in which the mechanism can move on the optical axis.

  In each embodiment, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves along a part of a convex locus on the image plane side.

  The second, third, and fourth lens units L2, L3, and L4 move to the object side during zooming from the wide-angle end to the telephoto end.

  The second lens unit L2 moves from the wide-angle end to the telephoto end so that the distance from the first lens unit L1 is narrower.

  The third lens unit L3 moves from the wide-angle end to the telephoto end so that the distance from the second lens unit L2 becomes wider.

  The fourth lens unit L4 moves from the wide-angle end to the telephoto end so that the distance from the third lens unit L3 is narrower.

  In Examples 1, 2, and 4, focusing is performed by moving the first lens unit L1. In Example 3, focusing is performed by moving two lenses on the image side among the four lenses constituting the first lens unit L1.

  In the zoom lens of each embodiment of the present invention, the back focus is the shortest at the wide angle end. Therefore, the refractive power arrangement is made such that the image-side principal point of the entire system is located on the image side so that the back focus at the wide-angle end becomes long. That is, at the wide angle end, the entire optical system is of a retrofocus type. Specifically, the second, third, and fourth lens units L2, L3, and L4 are arranged at positions away from the first lens unit L1 having a negative refractive power so that the combined refractive power becomes a positive refractive power. Yes.

  Further, the third lens unit L3 having a negative refractive power is arranged closer to the object side so that the image-side principal point of the synthesis of the second, third, and fourth lens units L2, L3, and L4 is arranged on the image side. Therefore, the back focus in the entire system is made sufficiently long.

In the zoom lens of the present invention, in order to ensure sufficient back focus, the focal length of the first lens unit L1 is f1, and the combined focal length from the second lens unit to the fourth lens unit at the wide angle end is f24. ,
0.5 <| f1 / f24 | <1.4 (1)
The following conditional expression is satisfied.

  If the upper limit of conditional expression (1) is exceeded, it will be difficult to obtain sufficient back focus. When the lower limit of conditional expression (1) is exceeded, the asymmetry of the refractive power arrangement before and after the stop SP becomes too large, and distortion and astigmatism are greatly generated.

  Desirably, conditional expression (1) should be in the following range.

0.6 <| f1 / f24 | <1.4 (1a)
More preferably, conditional expression (1) should be in the following range.

0.7 <| f1 / f24 | <1.2 (1b)
On the other hand, at the telephoto end, in order to shorten the total lens length (distance on the optical axis from the lens surface closest to the object side of the first lens group to the image plane), the entire optical system is more telephoto (telephoto type). It is trying to become. That is, positive and negative refractive powers are arranged in order from the object side to the image side so that the image-side principal point of the entire system is located closer to the object side.

  Specifically, at the zoom position at the telephoto end, the first lens unit L1 having a negative refractive power and the second lens unit L2 having a positive refractive power are brought close to each other, so that the first lens unit L1 and the second lens unit L2 The combined refractive power is positive. Further, the third lens unit L3 is brought close to the fourth lens unit L4, and the combined refractive power of the third lens unit L3 and the fourth lens unit L4 is made negative.

  This shortens the total lens length at the telephoto end by forming a telephoto type optical system.

  In the zoom lens of each embodiment of the present invention, in order to reduce fluctuations in distortion during zooming, the positive lens is located closest to the object side of the first lens unit L1 having a positive refractive power, and the fourth lens unit having a negative refractive power. A negative lens is disposed on the most image side of L4.

  In general, a zoom lens with negative, positive, negative, and positive refractive power lenses arranged in order from the object side to the image side has a strong retrofocus type in the entire system in order to secure a back focus longer than the focal length. Therefore, negative distortion is particularly large at the wide angle end. If this is corrected only with an aspherical surface, the amount of aspherical surface becomes large, and aberrations other than distortion such as astigmatism become worse.

  Therefore, in each embodiment of the present invention, in order to reduce the variation of distortion without deteriorating other aberrations, an aspherical surface is used instead of simply using an aspherical surface. The amount of distortion at the edges is reduced.

  Distortion is greatly generated at a position where the incident height (distance from the optical axis) h of the paraxial ray of the pupil to the lens surface increases. For this reason, the first lens unit L1 and the fourth lens unit L4 having negative refractive power are sandwiched by sandwiching the stop SP by using the most image side lens of the fourth lens unit L4 on the image side of the stop SP as a negative lens. Is a negative lens arranged on the most image side of the lens, and has a symmetrical refractive power arrangement so as to cancel the negative distortion generated in the first lens unit L1. Thereby, the distortion at the wide angle end can be greatly improved.

In the zoom lens of the present invention, when the focal length of the entire system at the wide-angle end is fw, and the radius of curvature of the negative lens disposed on the most image side of the fourth lens unit L4 is Rn,
0.50 <Rn / fw <15.0 (2)
The following conditional expression is satisfied.

  If the upper limit of conditional expression (2) is exceeded, the negative refracting power at the position where the incident height (distance from the optical axis) h of the paraxial ray of the pupil in the fourth lens unit L4 is the highest is insufficient. The negative distortion of the first lens unit L1 cannot be canceled out, and a large amount of negative distortion occurs at the wide angle end of the entire system. If the lower limit is exceeded, it is difficult to ensure the back focus.

  Desirably, conditional expression (2) should be in the following range.

0.65 <Rn / fw <10.0 (2a)
More preferably, conditional expression (2) should be in the following range.

0.70 <Rn / fw <5.0 (2b)
With the above configuration, the object of the present invention is achieved, but more desirably, the lens located on the most image side of the first lens unit L1 having the negative refractive power located on the most object side is constituted by a positive lens. It is preferable to act so as to cancel the negative distortion generated in the first lens unit L1.

  In addition, by adding an aspherical surface to the first lens unit L1 in which the incident height (distance from the optical axis) h of the pupil paraxial ray to the lens surface is increased, fluctuations in distortion can be further reduced. With the configuration of the present invention, the amount of variation in distortion can be reduced with respect to a conventional zoom lens, so even if an aspheric lens is used, it is not necessary to greatly increase the amount of the aspheric surface. It is possible to further reduce fluctuations in distortion without deteriorating other aberrations such as astigmatism.

  More preferably, an aspherical surface is used for the first lens unit L1 by adding an aspherical surface to the fourth lens unit L4 in which the incident height (distance from the optical axis) h of the paraxial ray of the pupil increases. As in the case of doing this, the variation in distortion can be further reduced.

More preferably, in order to cancel the strong negative distortion of the first lens unit L1, the refractive power of the negative lens disposed closest to the image side of the fourth lens unit L4 should be relatively large. Therefore, when the focal length of the negative lens located closest to the image side of the fourth lens unit L4 is fn and the focal length of the entire lens system at the wide angle end is fw,
0.3 <| fn / fw | <5.5 (3)
It is good to satisfy the condition.

  When the upper limit of conditional expression (3) is exceeded, it becomes difficult to cancel the negative distortion generated by the first lens unit L1. If the lower limit of conditional expression (3) is exceeded, it will be difficult to ensure the back focus.

  Desirably, conditional expression (3) should be in the following range.

0.4 <| fn / fw | <4.5 (3a)
More preferably, conditional expression (3) should be in the following range.

0.5 <| fn / fw | <3.0 (3b)
More preferably, the focal length of the positive lens closest to the object side arranged to reduce negative distortion generated by the first lens unit L1 having a negative refractive power is fp, and the focal length of the entire lens system at the wide angle end. Is fw,
3.0 <fp / fw <25.0 (4)
It is good to satisfy the condition.

  If the upper limit of conditional expression (4) is exceeded, it will be difficult to sufficiently correct the negative distortion generated by the first lens unit L1. Exceeding the lower limit of conditional expression (4) is not preferable because, at the wide angle end, distortion at the periphery of the screen is smaller than distortion at the intermediate angle of view, so-called Jinkasa-shaped distortion.

  Desirably, conditional expression (4) should be in the following range.

3.5 <fp / fw <22.5 (4a)
Desirably, conditional expression (4) should be in the following range.

4.0 <fp / fw <20.0 (4b)
More preferably, in order to make the negative lens arranged closest to the image side of the fourth lens unit L4 into a negative lens having strong refractive power, it is preferable to use a biconcave lens. Therefore, when the radius of curvature of the object side lens surface of the negative lens disposed closest to the image side of the fourth lens unit L4 is R1, and the radius of curvature of the image side lens surface is Rn,
−0.8 <(Rn + R1) / (Rn−R1) ≦ 0.18 (5)
It is good to satisfy the following conditional expression.

  When the upper limit of conditional expression (5) is exceeded, the refractive power of the lens surface on the image side of the negative lens disposed closest to the image side in the fourth lens unit L4 becomes small, and distortion of the entire system at the wide angle end is reduced. It becomes difficult. If the lower limit of conditional expression (5) is exceeded, it will be difficult to ensure the back focus.

  Desirably, conditional expression (5) should be in the following range.

−0.6 <(Rn + R1) / (Rn−R1) ≦ 0.18 (5a)
More preferably, conditional expression (5) should be in the following range.

−0.4 <(Rn + R1) / (Rn−R1) ≦ 0.18 (5b)
Next, numerical examples 1 to 4 of the zoom lens according to the present invention will be described.

  In Numerical Example 1, a part of the lens surface of the fourth lens unit L4 in which the incident height (distance from the optical axis) h of the paraxial ray of the pupil is increased to an aspheric surface, and distortion and astigmatism are reduced. It is corrected. In Numerical Examples 2, 3, and 4, some of the lens surfaces of the first lens unit L1 and the fourth lens unit L4 in which the incident height (distance from the optical axis) h of the paraxial ray of the pupil increases. By using an aspherical surface, distortion and astigmatism are corrected.

  In each numerical example, i indicates the order counted from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), and Di is the axis between the i-th surface and the (i + 1) -th surface. The upper spacing, Ni, and νi respectively indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line. f is a focal length, Fno is an F number, and ω is a half angle of view.

  Further, the aspherical shape is such that X is the amount of displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, r is the paraxial radius of curvature, k is the conic constant, A, When B, C, D, E... Are aspherical coefficients of respective orders,

で表す。なお、各非球面係数における「Ｅ±ＸＸ」は「×１０^±ＸＸ」を意味している。

Represented by Note that “E ± XX” in each aspheric coefficient means “× 10 ^{± XX} ”.

(Numerical example 1)
f = 28.7-78.0mm Fno = 3.63-4.67

Surface number rd nd vd Effective diameter
1 168.712 2.79 1.60311 60.6 46.54
2 -1409.596 0.15 45.55

3 76.198 1.8 1.8061 40.9 39.29
4 20.615 8.74 31.27
5 -89.856 1.5 1.60311 60.6 31.14
6 52.123 0.15 30.01
7 34.588 3.41 1.84666 23.9 30
8 112.149 (variable) 29.59
9 40.524 1 1.84666 23.9 22.99
10 20.176 5.73 1.6516 58.5 22.85
11 -73.421 0.15 22.99
12 23.335 2.59 1.744 44.8 22.89
13 35.222 (variable) 22.23
14 (Aperture) ∞ 1.03 20.8
15 -1690.03 3.47 1.69895 30.1 20.47
16 -23.867 1 1.6935 53.2 20.22
17 56.656 1.62 19.42
18 -68.778 1 1.65412 39.7 19.41
19 242.832 (variable) 19.51
20 * 57.877 3.49 1.6935 53.2 19.73
21 -31.079 0.15 19.73
22 60.493 3.91 1.65844 50.9 18.48
23 -22.327 1 1.7495 35.3 17.92
24 32.159 (variable) 17.63

Wide angle Medium Telephoto focal length 28.7 54.0 78.0
F number 3.63 4.15 4.67
Angle of view 37.01 21.82 15.5
Image height 21.64 21.64 21.64
Total lens length 126.39 120.68 131.55
BF 39.13 57.92 77.72

Variable interval Wide angle Medium telephoto
d8 32.2 9.38 2.17
d13 3.17 5.83 5.99
d19 7.2 2.86 1
d24 39.13 57.92 77.72
Each group focal length group Start surface Focal length
1 1 -39.50
2 9 31.74
3 14 -40.10
4 20 47.30

Aspheric coefficient 20th surface
KABCD
-3.454750E + 01 5.486680E-06 -8.389720E-08 1.214720E-10 1.001270E-12
E
-4.532080E-15
(Numerical example 2)
f = 28.7-78.0mm Fno = 3.63-4.67
Surface number rd nd vd Effective diameter
1 105.141 3.15 1.60311 60.6 45.18
2 500.793 0.15 43.90
3 173.870 1.80 1.69350 53.2 41.87
4 * 19.704 9.05 32.40
5 -139.908 1.50 1.65160 58.5 32.27
6 87.213 0.15 31.51
7 36.384 3.06 1.84666 23.9 31.31
8 83.722 (variable) 30.86
9 29.409 1.00 1.84666 23.9 23.34
10 17.540 5.69 1.60311 60.6 22.83
11 -304.363 0.15 22.89
12 31.442 2.67 1.77250 49.6 22.96
13 66.134 (variable) 22.50
14 (Aperture) ∞ 1.56 20.89
15 -97.627 3.87 1.76182 26.5 20.58
16 -18.057 1.00 1.65412 39.7 20.49
17 120.562 1.25 19.69
18 -64.919 1.00 1.74950 35.3 19.67
19 280.365 (variable) 19.72
20 * 55.780 3.36 1.69350 53.2 19.88
21 -34.726 0.15 19.85
22 56.668 3.86 1.61772 49.8 18.69
23 -28.384 1.00 1.74950 35.3 17.99
24 34.261 (variable) 17.19

Wide angle Medium Telephoto focal length 28.7 54.0 78.0
F number 3.63 4.15 4.67
Angle of view 37.01 21.83 15.5
Image height 21.64 21.64 21.64
Total lens length 127.92 122.14 133.3
BF 38.50 58.36 78.87

Variable interval Wide angle Medium telephoto
d8 33.40 9.48 1.68
d13 4.37 6.49 6.35
d19 6.24 2.42 1.00
d24 38.50 58.36 78.87

Each group focal length group Start surface Focal length
1 1 -40.52
2 9 33.75
3B 14 -45.67
4 20 50.19

Aspheric coefficient 4th surface
KABCD
-1.806350E-01 -2.177020E-07 -6.488410E-09 3.034060E-11 -1.415540E-13
E
1.127960E-16
20th page
KABCD
-2.201530E + 01 -2.551400E-06 -4.149010E-08 3.313000E-11 -5.285710E-13
E
4.577500E-15
(Numerical Example 3)
f = 28.7-68.0mm Fno = 2.92-2.92
Surface number rd nd vd Effective diameter
1 537.600 4.42 1.48749 70.2 71.65
2 -369.425 0.15 70.16
3 75.179 3.00 1.58313 59.4 55.99
4 * 27.421 20.52 44.32
5 -87.596 2.00 1.72916 54.7 37.08
6 51.582 0.15 34.46
7 48.875 3.71 1.84666 23.9 34.41
8 165.522 (variable) 33.81
9 137.725 1.50 1.84666 23.9 30.46
10 29.454 6.39 1.71300 53.9 31.48
11 -268.251 0.15 31.92
12 56.842 3.11 1.80 400 46.6 33.39
13 228.171 0.15 33.36
14 57.052 2.89 1.83400 37.2 33.49
15 154.384 (variable) 33.19
16 (Aperture) ∞ 1.88 29.23
17 -119.242 3.81 1.84666 23.9 28.97
18 -33.415 1.00 1.65412 39.7 28.93
19 183.882 1.61 28.23
20 -101.286 1.00 1.58913 61.1 28.22
21 141.337 (variable) 28.27
22 48.400 4.87 1.65 160 58.5 31.54
23 -123.253 0.15 31.71
24 -3161.136 3.08 1.72916 54.7 31.78
25 -66.197 0.15 31.83
26 * -1199.167 2.24 1.69350 53.2 31.38
27 -75.742 1.00 1.80518 25.4 31.32
28 82.653 (variable) 31.20

Wide angle Medium Telephoto focal length 28.7 50.0 68.0
F number 2.92 2.92 2.92
Angle of view 37.01 23.4 17.65
Image height 21.64 21.64 21.64
Total lens length 177.91 164.47 168.98
BF 46.71 62.02 75.33

Variable interval Wide angle Medium telephoto
d8 35.74 9.24 1.00
d13 1.87 10.54 16.04
d19 24.68 13.76 7.70
d24 46.71 62.02 75.33

Each group focal length group Start surface Focal length
1 1 -42.91
2 9 41.82
3 16 -66.18
4 22 54.92

Aspheric coefficient 4th surface
KABCD
-5.296450E-01 1.709810E-06 -1.696210E-10 1.126600E-11 -2.261180E-14
E
2.056540E-17
26th page
KABCD
-5.923000E + 03 -7.595530E-06 -1.131310E-09 -1.194530E-12 -4.479050E-14
E
1.259520E-16
(Numerical example 4)
f = 28.7-78.0mm Fno = 3.63-4.67
Surface number rd nd vd Effective diameter
1 101.856 3.58 1.60311 60.6 45.06
2 1636.818 0.15 43.74000
3 243.447 1.80 1.69350 53.2 41.64
4 * 19.636 8.83 31.97000
5 -140.683 1.50 1.65160 58.5 31.84
6 84.779 0.15 31.06000
7 35.906 3.01 1.84666 23.9 30.85
8 81.870 (variable) 30.39000
9 29.724 1.00 1.84666 23.9 23.33
10 17.661 5.67 1.60311 60.6 22.85
11 -299.477 0.15 22.92000
12 31.197 2.71 1.77250 49.6 23.02
13 67.131 (variable) 22.55000
14 (Aperture) ∞ 1.53 20.98000
15 -102.809 3.85 1.76182 26.5 20.68
16 -18.421 1.00 1.65412 39.7 20.58
17 123.048 1.25 19.77000
18 -64.945 1.00 1.74950 35.3 19.75
19 248.304 (variable) 19.80000
20 * 55.718 3.38 1.69350 53.2 19.96
21 -34.563 0.15 19.93000
22 56.110 3.82 1.61772 49.8 18.75
23 -29.514 1.00 1.74950 35.3 18.05
24 33.616 (variable) 17.20000

Wide angle Medium Telephoto focal length 28.7 54.0 78.0
F number 3.63 4.15 4.67
Angle of view 37.01 21.83 15.5
Image height 21.64 21.64 21.64
Total lens length 130.7 125.39 136.74
BF 38.73 58.58 79.12

Variable interval
d8 32.98 9.53 1.90
d13 4.06 6.30 6.20
d19 6.40 2.46 1.00
d24 38.73 58.58 79.12

Each group focal length group Start surface Focal length
1 1 -40.02
2 9 33.56
3 14 -45.79
4 20 50.20

Aspheric coefficient 4th surface
KABCD
-1.861930E-01 -1.662510E-08 -4.939090E-09 2.532120E-11 -1.282500E-13
E
1.251010E-16
20th page
KABCD
-2.230880E + 01 -2.446400E-06 -4.411920E-08 4.668810E-11 -4.315080E-13
E
3.705100E-15

  FIG. 9 shows a camera (imaging device) using the zoom lens shown in the first to fourth embodiments, and the zoom lens 11 shown in the first to fourth embodiments is incorporated in the lens barrel 10. Yes. In the camera body 20, a mirror 21 that reflects upward the light beam captured by the zoom lens 11, a focusing plate 22 on which a subject image is formed by the zoom lens 11, and a pentagon that converts the light beam from the focusing plate 22 into an erect image. A roof prism 23, an eyepiece 24 for observing a subject image formed on the focusing screen 22, a solid-state image sensor (photoelectric conversion element) 25 such as a CCD sensor or a CMOS sensor for receiving a light beam from the zoom lens 11, and the like are provided. It has been.

  FIG. 9 shows the observation state, that is, the photographing standby state. When the photographer operates the release button, the mirror 21 is retracted from the illustrated optical path, and the subject image is captured on the solid-state image sensor 25. Thus, by using the zoom lens shown in Embodiments 1 to 4 for a camera, a camera having high optical performance can be realized.

FIG. 3 is a lens cross-sectional view at the wide-angle end of the zoom lens according to the first exemplary embodiment of the present invention. Aberration diagram in the infinite focus state of Example 1 of the present invention Sectional view of the zoom lens of Embodiment 2 of the present invention at the wide-angle end Aberration diagram of the zoom lens according to Example 2 of the present invention in an infinitely focused state Lens cross-sectional view at the wide-angle end of the zoom lens according to Embodiment 3 of the present invention. Aberration diagram of the zoom lens according to Example 3 of the present invention in an infinitely focused state Lens cross-sectional view at the wide-angle end of the zoom lens according to the fourth exemplary embodiment of the present invention. Aberration diagram in the infinite focus state of the zoom lens according to the fourth exemplary embodiment of the present invention. 1 is a schematic configuration diagram of a camera using zoom lenses according to first to fourth embodiments of the present invention.

Explanation of symbols

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group SP Aperture stop IP Image surface C. Sine condition dd line g g line S sagittal image plane M meridional image plane Fno F number ω angle of view

Claims (6)

In order from the object side to the image side, a first lens unit having a negative refractive power, a second lens unit having positive refractive power, a third lens unit having a negative refractive power and a fourth lens unit having a positive refractive power hand in zooming from the wide-angle end to the telephoto end, the interval between groups adjacent lens is changed, the zoom lens interval becomes smaller in the second lens group and the third lens group, the most object of the first lens group A positive lens on the side, a negative lens on the most image side of the fourth lens group, the focal length of the first lens group is f1, and from the second lens group to the fourth lens group at the wide-angle end F24, the focal length of the entire system at the wide-angle end is fw, the radius of curvature of the lens surface on the image side of the negative lens disposed closest to the image side of the fourth lens group is Rn , and the fourth lens group The lens surface on the object side of the negative lens located closest to the image side When the radius of curvature of R1 is R1,
0.5 <| f1 / f24 | <1.4
0.50 <Rn / fw <15.0
−0.8 <(Rn + R1) / (Rn−R1) ≦ 0.18
A zoom lens satisfying the following conditional expression: When the focal length of the negative lens arranged closest to the image side of the fourth lens group is fn,
0.3 <| fn / fw | <5.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the positive lens disposed closest to the object side of the first lens group is fp,
3.0 <fp / fw <25.0
The zoom lens according to claim 1, wherein the following conditional expression is satisfied. The first lens group zoom lens according to any one of claims 1 to 3, characterized in that it comprises at least one aspherical surface. The fourth lens group zoom lens according to any one of claims 1 to 4, characterized in that it comprises at least one aspherical surface. A zoom lens according to any one of claims 1 to 5, an imaging apparatus characterized by having a solid-state imaging device for receiving the image formed by the zoom lens.

Images