JP6276634B2 - Super wide-angle zoom lens - Google Patents

Description

  The present invention relates to an optical system suitable for a photographic lens used in an imaging apparatus such as a still camera or a video camera, and employs an inner focus system suitable for an autofocus camera, and a focus lens group in a direction along the optical axis. The present invention relates to a zoom lens that has a small image height change rate when it is vibrated (wobbling) and has a wide field angle of 120 ° or more at the wide angle end.

  A zoom lens focusing method is generally a front focusing method in which the first group on the object side is extended as it is. However, due to the demand for AF, an inner focus method in which focusing is performed with a relatively light lens group other than the first group has been desired. In recent years, there have been many proposals for this inner focus method, but a correction cam is required to prevent a focus shift during zooming at a finite distance, and the mechanism is complicated. Patent Documents 1, 2, 3, and 4 are disclosed as techniques that employ an inner focus method in which focusing is performed using a lens group other than the first group.

Japanese Patent Laid-Open No. 4-15612 JP-A-6-230281 JP 2001-188171 A (Patent No. 4519232) JP 2013-15621 A

  The zoom type preceded by a lens unit having a negative refractive power is a type suitable for wide-angle zoom and ultra-wide-angle zoom. However, focusing is often performed with the first lens group, and the focus group is heavy, which hinders AF.

  Further, there are some lenses that achieve a slight weight reduction by focusing the inside of the first lens group, but the weight has not been reduced sufficiently. For this reason, in order to improve the downsizing of the actuator and the problems of responsiveness and real-time characteristics, it is necessary to further reduce the weight of the focus group.

  In addition, like the auto focus of mirrorless interchangeable-lens cameras that have emerged in recent years, the focus lens group continues to be slightly oscillated (wobbling) in the direction along the optical axis, thereby constantly determining the focus drive direction. Focus methods have been developed. At that time, if the image height change rate during wobbling is large, the viewer recognizes the magnification change of the subject on the screen and feels it annoying. Therefore, a focus type having a small image height change rate with respect to the focus change has been desired.

Here, given a predetermined object height, the image height in the focused state corresponding to the object is y, the focus lens group is moved without changing the shooting distance and the object height, and the Gaussian image plane is focused. When the movement in the optical axis direction from the position of the state is Δs, the image height when moving by Δs = ± 0.08 mm is y ′. Δs = ± 0.08 mm corresponds to the one-side depth of focus when the diameter of the minimum circle of confusion is 0.01 mm and the F value is F8. Here, η defined by the following equation is called an image height change rate.
η = (y′−y) / y Reference formula (1)

Regarding the target value of the image height change rate η, Japanese Unexamined Patent Application Publication No. 2009-122620 has the following description, and the present invention sets the target of the image height change rate η with reference to this description. When the amount of movement of the Gaussian image plane is Δs, paragraphs [0060] and [0062] “Here, E is defined as follows.
E = η / Δs
Various experiments were conducted, and the conditions under which image height change was not noticeable under general conditions were
| E | <1/8
The conditions under which the change in image height is not noticeable under the most severe conditions are
| E | <1/80
I found out that "
From this description, the allowable image height change rate η when Δs = 0.08 is
| Η | = E × Δs
The conditions under which the change in image height is not noticeable under the most severe conditions are
| Η | <0.001 (0.1%)
Therefore, the present invention sets the target of the image height change rate η with reference to this description.

  The zoom lens disclosed in Patent Document 1 includes a first group having a negative refractive power and a second group having a positive refractive power, and is the first in a two-group zoom lens that performs zooming by moving both lens groups. One group is divided into two lens groups having a negative refractive power, and a small and light negative group 12 having a negative refractive power on the image plane side is moved on the optical axis to perform focusing, thereby achieving high-speed focusing operation. It is said that a zoom lens with a wide field angle of about 113 degrees at the wide-angle end that makes it easy to achieve will be achieved, but the focus group is composed of a plurality of lenses and has a negative refractive power as a whole Since it is a group, weight reduction of the focus lens group is not sufficient.

  Further, at the wide angle end of Example 1 of Patent Document 1, the value of the image height change rate η described above is as large as 0.51% at the maximum image height 21.63, and the photographing field angle at the wide angle end is 113. There is only a degree.

  In addition, the zoom lens disclosed in Patent Document 2 includes three lens groups of a first group having a negative refractive power, a second group having a negative refractive power, and a third group having a positive refractive power in order from the object side. In this technique, the focus group is composed of a plurality of lenses as in the case of Patent Document 1, and the focus group is a small and light second group. Since the lens group has a refractive power, weight reduction of the focus lens group is not sufficient.

  In Example 1 of Patent Document 2, the image height change rate η at the wide-angle end is as large as 0.20% at the maximum image height 21.63, and the photographing field angle at the wide-angle end is only about 93 degrees.

  Further, the zoom lens disclosed in Patent Document 3 includes four groups of negative, negative, positive and positive in order from the object side. When focusing from an infinite object distance to a close object, the third lens group L3 is in the image plane direction. The zoom lens with the wide angle of view that is optimal for inner focus can be obtained by appropriately setting the power of the third lens group and the magnification of the third and fourth lens groups. Is only about 78 degrees, and the angle of view is not sufficient.

  Further, the lens disclosed in Patent Document 4 includes, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. The first A lens group G1A having a negative refractive power and the first B lens group G1B having a negative refractive power are moved to the object side during focusing, and a predetermined conditional expression is satisfied, Providing a high-performance ultra-wide-angle lens system that is suitable for 35mm format interchangeable lenses with a long back focus and a large image circle, and has a small aberration fluctuation due to focusing. doing.

  However, in this technique as well, as in Patent Documents 1 and 2, since the focus group is a lens group having a negative refractive power as a whole composed of a plurality of lenses, weight reduction of the focus lens group is not sufficient.

  Example 1 of Patent Document 4 is a single focus lens, but the image height change rate η is as large as −0.37% at the maximum image height 21.63.

  In Example 2 which is a zoom lens disclosed in Patent Document 4, the image height change rate η at the wide-angle end has a larger problem of −0.7% at the maximum image height 21.63.

  The present invention has been made to solve the above-described problems of the prior art, and by appropriately setting the power arrangement, the focus lens group can be reduced in weight, and the angle of view is optimal for inner focus with a small image height change rate. The purpose is to provide a zoom lens with a wide angle of view that exceeds 100 degrees.

In order to solve the above-described problem, in the super wide-angle zoom lens according to the first aspect of the invention, in order from the object side, the first lens group G1 having negative power, the second lens group G2 including a single lens having positive power, and the third lens having positive power It is composed of a group G3, a positive power fourth lens group G4, and a positive power fifth lens group G5. When focusing from an object side infinity to a short distance object, the second lens group G2 moves in the image plane direction and changes When magnifying, the distance between the lens groups of the second lens group G2 to the fifth lens group G5 changes, and the second lens group G2 at the wide-angle end with respect to the object side surface of the second lens group G2. When the image position of the stop by the combining optical system on the surface from the front to the stop is FcEntp, the following conditions are satisfied.
(1) 10.0 <f2 / fw <40.0
(2) 1.0 <1 / (MRT ^ 2 × (M2T ^ 2-1))
(3) 0.1 <FcEntp / f2 <0.5
(4) 2.5 <FcEntp / fw
However,
fw: focal length at the wide end infinity f2: focal length of the second lens group M2T: magnification burden of the second lens group at the telephoto end when the object distance is infinity MRT: third telephoto end at the object distance infinity Composite magnification burden from the lens group to the fifth lens group

  In the super wide-angle zoom lens of the second invention, in the first invention, the first lens group G1 is fixed with respect to the image plane at the time of zooming.

  According to the present invention, a focus lens group is reduced in weight by appropriately setting a power arrangement, and a zoom lens having a wide angle of view exceeding 120 degrees and optimal for inner focus with a small image height change rate is provided. be able to.

It is a lens block diagram at the time of wide-angle end of the imaging optical system of Example 1 of this invention at the time of infinity focusing. FIG. 4 is a longitudinal aberration diagram of an object at infinity according to Example 1 of the present invention, in which a is the wide-angle end, b is the intermediate focal length (17.54 mm), and c is the aberration diagram at the telephoto end. FIG. 4 is a lateral aberration diagram of an object at infinity according to Example 1 of the present invention, where a is the wide-angle end, b is the intermediate focal length (17.54 mm), and c is the aberration diagram at the telephoto end. FIG. 4 is a longitudinal aberration diagram at an object distance of 400 mm in Example 1 of the present invention, where a is an aberration angle at the wide angle end, b is an intermediate focal length (17.54 mm), and c is an aberration diagram at the telephoto end. FIG. 4 is a lateral aberration diagram at an object distance of 400 mm according to Example 1 of the present invention, where a is the wide-angle end, b is the intermediate focal length (17.54 mm), and c is the aberration diagram at the telephoto end. It is a lens block diagram at the time of wide-angle end of the imaging optical system of Example 2 of this invention at the time of infinity focusing. FIG. 6 is a longitudinal aberration diagram of an object at infinity according to Example 2 of the present invention, in which a is the wide-angle end, b is the intermediate focal length (16.45 mm), and c is the telephoto end aberration diagram. FIG. 6 is a lateral aberration diagram for an object at infinity according to Example 2 of the present invention, where a is the wide-angle end, b is the intermediate focal length (16.45 mm), and c is the aberration diagram at the telephoto end. FIG. 6 is a longitudinal aberration diagram at an object distance of 400 mm in Example 2 of the present invention, where a is an aberration angle at a wide angle end, b is an intermediate focal length (16.45 mm), and c is an aberration diagram at a telephoto end. FIG. 7 is a lateral aberration diagram at an object distance of 400 mm in Example 2 of the present invention, where a is an aberration angle at the wide angle end, b is an intermediate focal length (16.45 mm), and c is an aberration diagram at the telephoto end.

  The super wide-angle zoom lens according to the present invention includes, in order from the object side, a first lens group G1 having negative power, a second lens group G2 including a single lens having positive power, a third lens group G3 having positive power, and a fourth lens having positive power. The lens group G4 includes a positive power fifth lens group G5, and the second lens group G2 moves in the image plane direction when focusing from an object-side infinity object to a short-distance object.

  In the super wide-angle zoom lens according to the present embodiment, when focusing from an object side infinity to a close object, the second lens group G2, which is a single lens, moves in the image plane direction, so that the load on the actuator related to focusing is reduced. Therefore, it is possible to realize a high-speed focusing operation with a small amount, and to reduce the fluctuation of the image height due to the focusing. Further, by making the second lens group G2 a single lens of positive power, the focusing actuator can be made compact, and the entire optical system can be made compact.

Also, in order to realize high-speed focusing operation and downsizing of the optical system, when the focal length at the wide end infinity is fw and the focal length of the second lens group is f2, the following conditional expression must be satisfied: It is characterized by.
(1) 10.0 <f2 / fw <40.0
However,
fw: focal length at wide end infinity f2: focal length of second lens group

In addition, in order to drive and control the second lens group, which is the focus lens group, within the AF focusing range, it is important to define the magnification burden for the second lens group and the second lens group and subsequent objects. When the magnification burden of the second lens group at the telephoto end at the infinite distance is M2T and the combined magnification burden MRT from the third lens group on the telephoto side to the fifth lens group at the object distance infinite is MRT, the following conditional expression It is characterized by satisfying.
(2) 1.0 <1 / (MRT ^ 2 × (M2T ^ 2-1))
However,
M2T: magnification burden of the second lens group at the telephoto end when the object distance is infinity MRT: synthetic magnification burden from the third lens group to the fifth lens group at the telephoto end when the object distance is infinity

Another object of the present invention is to suppress image height fluctuations due to wobbling. Image height variation due to wobbling can be represented by variation in distortion due to wobbling.

According to Yoshiya Matsui, lens design method, Kyoritsu Shuppan P88, the third-order distortion coefficient V is expressed by the following equation.
V = J ・ IV
When expanded, it becomes the following,
V = (H ′ · Q ′) ^ 3 / (H · Q) · H ^ 2 · Δ (1 / (n · s)) + P · (H′h · Q ′) / (H · Q) Reference equation (2)
The third-order distortion coefficient V is proportional to the cube of the paraxial principal ray height H ′.

  Accordingly, in order to reduce the variation in distortion due to the wobbling, the variation in the principal ray height of the focus lens group due to the wobbling may be reduced.

Here, the position of the aperture image by the focus lens group at the infinite object distance, the magnification burden of the second lens group that is the focus lens group, the third lens group that is the lens group behind the focus lens group, and the fifth lens group. From the combined magnification burden up to the lens group and the principal ray height in the focus lens group, the fluctuation Δh of the principal ray height of the focus lens group due to wobbling is expressed by the following equation.
Δh = h′−h = h · Δs / (FcEntp × MR ^ 2 × (M2 ^ 2-1)) Reference formula (3)
However,
FcEntp: Image position of the aperture by the combining optical system of the surface from the second lens group G2 at the wide-angle end to the front of the aperture when the object distance is infinity: Image plane movement amount during wobbling h: Focus when the object distance is infinity The principal ray height h ′ in the lens group: the principal ray height M2 in the focus lens group at the time of wobbling: the magnification burden of the second lens group when the object distance is infinity MR: the third to fifth lenses when the object distance is infinity Composite magnification burden to group

  For this reason, in order to reduce the fluctuation of the chief ray height, it is understood that the position of the aperture image by the focus lens group when the object distance is infinite may be increased.

Therefore, in the present invention, the image position of the stop by the combining optical system of the surface from the second lens group G2 at the wide angle end to the front of the stop is set with reference to the object side surface of the second lens group G2, which is the focus lens group. This is achieved by satisfying the following conditions when FcEntp is used.
(3) 0.1 <FcEntp / f2 <0.5
(4) 2.5 <FcEntp / fw

  Further, at the time of zooming, the first lens group may be fixed or moved with respect to the image plane.

  Hereinafter, conditional expressions of the present invention will be described.

  Conditional expression (1) defines the focal length of the second lens group, which is the focus lens group, and is a condition for realizing high-speed focusing operation and downsizing of the optical system. When the lower limit of conditional expression (1) is exceeded and the focal length f2 of the second lens group G2 is shortened, the amount of extension for focusing becomes too short, and it becomes difficult to stop the focus lens group at an accurate in-focus position. .

  If the upper limit of conditional expression (1) is exceeded and the focal length f2 of the second lens group G2 is increased, the amount of extension for focusing becomes longer, and it is difficult to secure a space between the second lens group and the third lens group. The zoom ratio is inevitable. Moreover, since it is disadvantageous for compactization, a filter diameter becomes large. In addition, regarding the conditional expression (1), the lower limit value is further set to 14 and the upper limit value is further set to 19, whereby the above-described effect can be further ensured.

  Conditional expression (2) defines the sensitivity of the image plane when the second lens group G2 moves during focusing. If the lower limit of conditional expression (2) is exceeded, the amount of movement of the focus lens group decreases, so that the image plane moves greatly due to a slight movement of the focus lens group, and the second focus lens group is within the AF focusing range. It becomes difficult to drive and control the lens group G2. In addition, regarding the conditional expression (2), when the lower limit value is further set to 1.1, the above-described effect can be further ensured.

  Conditional expressions (3) and (4) are conditions for suppressing fluctuations in image height during wobbling. If the lower limit of conditional expression (3) is exceeded and the distance from the second lens group G2 at the wide-angle end to the image position of the stop by the combining optical system on the surface before the stop becomes small, the chief ray of the focus lens group during wobbling Since the fluctuation of the height becomes large, it becomes difficult to suppress the fluctuation of the image height during wobbling.

  If the distance from the second lens group G2 at the wide-angle end to the front of the stop increases beyond the upper limit of the conditional expression (3) and the image position of the stop by the combining optical system increases, the distance from the focus lens group to the stop is increased. Since the distance becomes large, the optical total length at the wide angle end becomes long, and it becomes difficult to increase the filter diameter and to secure the peripheral light amount. Also, if the focal length of the second lens group G2 is shortened, the negative refractive power of the composite system of the first and second lens groups is weakened, so that the back focus is shortened, and quick use when mounted on a single-lens reflex camera is used. It becomes difficult to suppress interference with the return mirror. For conditional expression (3), the lower limit value is further set to 0.19, and the upper limit value is further set to 0.29, whereby the above-described effect can be further ensured.

  When the lower limit of conditional expression (4) is exceeded and the distance from the second lens group G2 at the wide-angle end to the image position of the stop by the combining optical system on the surface from the front to the stop becomes small, the focus lens group at the time of wobbling is reduced. Since the variation in chief ray height becomes large, it becomes difficult to suppress the variation in image height during wobbling. In addition, regarding the conditional expression (4), by further setting the lower limit value to 3.6, the above-described effect can be further ensured.

  Next, a lens configuration of an example according to the imaging optical system of the present invention will be described. In the following description, the lens configuration is described in order from the object side to the image side.

  FIG. 1 is a lens configuration diagram when focusing on infinity at the wide angle end of the imaging optical system according to Example 1 of the present invention. In order from the object side, the first lens group G1 with negative power, the second lens group G2 composed of a single lens with positive power, the third lens group G3 with positive power, the fourth lens group G4 with positive power, and the fifth lens with positive power. Consists of a group G5, and the first lens group G1 is fixed with respect to the image plane during zooming.

  The first lens group G1 includes a negative meniscus lens having a convex surface facing the object side, an object-side surface having an aspheric shape and a negative meniscus lens having a convex surface facing the object side, and the object-side surface having an aspheric shape facing the object side A negative meniscus lens having a convex surface, an object-side surface having an aspherical shape and a biconcave negative lens, and a positive meniscus lens having a convex surface facing the object side.

  The second lens group G2 includes a positive meniscus lens having a convex surface directed toward the object side.

  The third lens group G3 includes a positive meniscus lens having a convex surface facing the object side, an aperture stop, a cemented negative lens composed of a biconvex lens and a biconcave lens, a negative meniscus lens having a concave surface facing the object side and the biconvex lens, It consists of a cemented positive lens.

  The fourth lens group G4 is composed of a cemented positive lens and a biconvex lens each composed of a biconvex lens and a negative meniscus lens having a concave surface directed toward the object side.

  The fifth lens group G5 includes a cemented negative lens composed of a negative meniscus lens having a convex surface directed toward the object side and a biconvex lens, a biconvex lens, and a positive surface having an aspheric surface on the object side and a concave surface directed toward the object side. It consists of a meniscus lens.

  FIG. 6 is a lens configuration diagram at the wide-angle end of the imaging optical system according to Example 2 of the present invention when focusing on infinity. In order from the object side, the first lens group G1 with negative power, the second lens group G2 composed of a single lens with positive power, the third lens group G3 with positive power, the fourth lens group G4 with positive power, and the fifth lens with positive power. It consists of group G5.

  The first lens group G1 includes a negative meniscus lens having a convex surface facing the object side, an object-side surface having an aspheric shape and a negative meniscus lens having a convex surface facing the object side, and the object-side surface having an aspheric shape facing the object side A negative meniscus lens having a convex surface and an object-side surface having an aspherical shape, a biconcave negative lens, and a biconvex lens.

  The second lens group G2 is composed of a biconvex lens.

  The third lens group G3 includes a positive meniscus lens having a convex surface directed toward the object side, an aperture stop, a cemented negative lens including a biconvex lens and a negative meniscus lens having a concave surface directed toward the object side, and the biconvex lens and the object side. It consists of a cemented positive lens consisting of a negative meniscus lens with a concave surface.

  The fourth lens group G4 is composed of a cemented positive lens and a biconvex lens each composed of a biconvex lens and a negative meniscus lens having a concave surface directed toward the object side.

  The fifth lens group G5 is composed of a cemented positive lens composed of a biconcave lens and a biconvex lens, and a positive meniscus lens having an aspheric surface on the object side and facing the convex surface on the object side.

  In the present invention, the focus lens group is composed of a single lens having a positive refractive power. However, one or both surfaces of the lens are made aspherical to improve the correction capability for spherical aberration, astigmatism, etc., or diffractive optics. It is also possible to increase the chromatic aberration correction capability by adding an element. In addition, although the weight of the focus lens group is increased, when importance is placed on the suppression of chromatic aberration fluctuations during focusing, a negative lens can be joined to the focus lens group to improve the chromatic aberration ability.

  Further, it is possible to move the focus lens in the optical axis direction at the time of zooming to give a degree of freedom for aberration correction, and to achieve higher performance and compactness.

  Specific numerical data of each embodiment of the imaging optical system of the present invention described above will be shown below.

  In [Surface data], the surface number is the number of the lens surface or aperture stop counted from the object side, r is the radius of curvature of each surface, d is the distance between the surfaces, nd is the refractive index with respect to the d-line (wavelength 587.56 nm). , Vd indicate Abbe numbers for the d line.

  The * (asterisk) attached to the surface number indicates that the lens surface shape is an aspherical surface. BF represents back focus.

  The (diaphragm) attached to the surface number indicates that the aperture stop is located at that position. ∞ (infinity) is entered in the radius of curvature for a plane or aperture stop.

  In [Aspherical data], each coefficient value giving the aspherical shape of the lens surface marked with * in [Surface data] is shown. As for the aspherical shape, the aspherical shape is y for the displacement from the optical axis in the direction perpendicular to the optical axis, z for the displacement (sag amount) in the optical axis direction from the intersection of the aspherical surface and the optical axis, and the reference When the radius of curvature of the spherical surface is r, the conic coefficient is K, 4, 6, 8, 10, and 12th order aspherical coefficients are A4, A6, A8, A10, and A12, respectively, the coordinates of the aspherical surface are given by the following equations. Shall be represented.

  [Various data] shows values such as the zoom ratio and the focal length in each focal length state.

  [Variable interval data] shows the variable interval and BF values at infinity and an object distance of 400 mm in each focal length state.

  [Lens Group Data] indicates the surface number of the most object side constituting each lens group and the combined focal length of the entire group.

  In all the values of the following specifications, the focal length f, the radius of curvature r, the lens surface interval d, and other length units described are in millimeters (mm) unless otherwise specified. In the system, the same optical performance can be obtained even in proportional expansion and proportional reduction, and the present invention is not limited to this.

  In addition, a list of corresponding values of the conditional expressions in each of these examples is shown.

  In the aberration diagrams corresponding to each example, d, g, and C represent d-line, g-line, and C-line, respectively, and ΔS and ΔM represent sagittal image plane and meridional image plane, respectively. .

Numerical example 1
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 42.6615 1.9704 1.91082 35.25
2 24.2589 7.7786
3 * 71.1417 2.5926 1.69350 53.20
4 21.3580 7.9778
5 * 53.0027 1.5556 1.69350 53.20
6 25.4724 9.2470
7 * -42.2927 1.4519 1.69350 53.20
8 25.7580 0.7855
9 30.6075 4.8928 2.00099 29.14
10 -969.7151 (d10)
11 74.0379 2.3524 1.43700 95.10
12 258.9689 (d12)
13 12.3999 2.0085 1.58144 40.89
14 31.3710 8.2485
15 (Aperture) ∞ 1.8232
16 21.5847 3.4542 1.43700 95.10
17 -10.1513 0.8296 2.00099 29.14
18 42.3225 1.8107
19 62.5186 3.5745 1.84666 23.78
20 -12.2007 0.8296 1.91082 35.25
21 -38.3977 d (21)
22 45.3792 5.5403 1.43700 95.10
23 -27.7586 0.8815 1.91082 35.25
24 -40.7253 0.1556
25 1409.8920 3.2356 1.43700 95.10
26 -60.5775 (d26)
27 518.1605 0.9334 1.88300 40.80
28 26.8496 5.8970 1.43700 95.10
29 -636.2727 0.2000
30 169.3387 4.7364 1.43700 95.10
31 -43.7886 0.7187
32 * -2681.9120 2.9580 1.48749 70.44
33 -69.6139 (BF)
Image plane ∞


[Aspherical data]
3 surfaces 5 surfaces 7 surfaces 32 surfaces
K 0.0000 8.1442 0.0000 0.0000
A4 4.06850E-05 -3.28812E-05 -3.20122E-06 -6.72992E-06
A6 -1.11106E-07 2.72667E-07 -7.81243E-08 -7.55005E-09
A8 2.19493E-10 -8.59851E-10 5.85250E-10 8.30127E-11
A10 -2.59322E-13 1.23561E-12 -1.55923E-12 -3.17695E-13
A12 1.29878E-16 -4.33546E-16 0.00000E + 00 3.29499E-16


[Various data]
Zoom ratio 1.67
Wide angle Medium telephoto Focal length 12.37 17.54 20.66
F number 4.59 5.26 5.82
Full angle of view 2ω 122.90 100.44 90.88
Image height Y 21.63 21.63 21.63
Total lens length 160.77 160.76 160.79


[Variable interval data]
Wide angle Medium telephoto
d0 ∞ ∞ ∞
d10 1.0371 1.0371 1.0371
d12 22.6186 8.1934 4.4958
d21 9.8389 7.6682 3.4347
d26 0.9334 9.3131 10.9894
BF 37.9000 46.1060 52.3923

Wide angle Medium telephoto
d0 239.2321 239.2421 239.2106
d10 3.5709 3.5708 3.5711
d12 20.0847 5.6596 1.9618
d21 9.8389 7.6682 3.4347
d26 0.9334 9.3131 10.9894
BF 37.9000 46.1061 52.3922


[Lens group data]
Group Start surface Focal length
G1 1 -13.18
G2 11 236.34
G3 13 60.21
G4 22 45.86
G5 27 141.18

Numerical example 2
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 42.6615 1.9704 1.91082 35.25
2 24.2589 7.9024
3 * 63.3459 2.5926 1.69350 53.20
4 20.6293 8.5222
5 * 53.4016 1.5556 1.69350 53.20
6 24.1538 9.0249
7 * -39.1052 1.4519 1.69350 53.20
8 37.9077 0.1556
9 39.8151 4.8928 2.00099 29.14
10 -200.4439 (d10)
11 118.1816 2.6653 1.43700 95.10
12 -223.0393 (d12)
13 13.6511 1.7620 1.58144 40.89
14 28.3671 7.4043
15 (Aperture) ∞ 1.8232
16 38.0088 7.9997 1.43700 95.10
17 -10.4450 0.8296 2.00099 29.14
18 -51.3776 1.8107
19 335.0939 3.7267 1.84666 23.78
20 -11.9924 0.8296 1.91082 35.25
21 -91.0165 (d21)
22 64.2667 6.2009 1.43700 95.10
23 -19.1834 0.8815 1.91082 35.25
24 -26.5088 0.1556
25 547.1739 3.2356 1.43700 95.10
26 -53.5186 (d26)
27 -70.6356 0.9334 1.88300 40.80
28 69.9939 7.7857 1.43700 95.10
29 -25.0068 0.7187
30 * 120.2835 0.8000 1.48749 70.44
31 422.2449 (BF)
Image plane ∞


[Aspherical data]
3 surfaces 5 surfaces 7 surfaces 30 surfaces
K 0.0000 8.2185 0.0000 0.0000
A4 3.15340E-05 -2.18619E-05 -3.07326E-07 -1.62938E-05
A6 -1.00251E-07 2.38636E-07 -8.73288E-08 -9.58513E-09
A8 2.19493E-10 -9.46629E-10 6.95034E-10 -1.49508E-11
A10 -2.59322E-13 1.56361E-12 -1.88585E-12 -2.41711E-14
A12 1.29878E-16 -8.09495E-16 0.00000E + 00 -2.09364E-16


[Various data]
Zoom ratio 1.71
Wide angle Medium telephoto Focal length 12.42 16.45 21.29
F number 4.66 5.08 5.76
Full angle of view 2ω 122.65 105.27 88.75
Image height Y 21.63 21.63 21.63
Total lens length 162.00 157.25 157.07


[Variable interval data]
Wide angle Medium telephoto
d0 ∞ ∞ ∞
d10 1.0371 1.0371 1.0371
d12 25.9545 11.9967 3.7956
d21 8.2892 6.9493 3.4347
d26 0.9334 6.8446 11.5632
BF 38.1549 42.7922 49.6113

Wide angle Medium telephoto
d0 238.0000 242.7492 242.9272
d10 3.0529 3.0178 3.0165
d12 23.9386 10.0160 1.8162
d21 8.2892 6.9493 3.4347
d26 0.9334 6.8446 11.5632
BF 38.1550 42.7921 49.6111


[Lens group data]
Group Start surface Focal length
G1 1 -13.67
G2 11 177.19
G3 13 63.22
G4 22 40.19
G5 27 271.94

[Values for conditional expressions]
Conditional expression / Example 1 2
(1) 10.0 <f2 / fw <40.0 19.11 14.26
(2) 1.0 <1 / (MRT ^ 2 × (M2T ^ 2-1)) 1.61 1.19
(3) 0.1 <FcEntpW / f2 <0.5 0.20 0.28
(4) 2.5 <FcEntpW / fw 3.75 4.02

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group S Aperture stop I Image surface

Claims (2)

In order from the object side, the first lens group G1 with negative power, the second lens group G2 composed of a single lens with positive power, the third lens group G3 with positive power, the fourth lens group G4 with positive power, and the fifth lens with positive power. The second lens group G2 is composed of the group G5, and when focusing from an object side infinity to an object at a short distance, the second lens group G2 to the fifth lens group G5 move when the second lens group G2 moves in the image plane direction and changes magnification. The distance between the lens groups of the lens groups changes, and the aperture of the surface from the second lens group G2 at the wide-angle end to the front of the aperture is determined by the combining optical system with reference to the object side surface of the second lens group G2. An ultra-wide-angle zoom lens satisfying the following conditions when the image position of FcEntp is:
(1) 10.0 <f2 / fw <40.0
(2) 1.0 <1 / (MRT ^ 2 × (M2T ^ 2-1))
(3) 0.1 <FcEntp / f2 <0.5
(4) 2.5 <FcEntp / fw
However,
fw: focal length at the wide end infinity f2: focal length of the second lens group M2T: magnification burden of the second lens group at the telephoto end when the object distance is infinity MRT: third telephoto end at the object distance infinity Composite magnification burden from the lens group to the fifth lens group   2. The super wide-angle zoom lens according to claim 1, wherein the first lens group G1 is fixed with respect to the image plane during zooming.

Images