JP2016102809A - Zoom lens, optical device, and zooming method of zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a zoom lens that is compact and offers wider view angle at the wide-angle end as well as a high zoom ratio; an optical device; and a zooming method of the zoom lens.SOLUTION: A zoom lens comprises a first lens group G1 having negative refractive power, second lens group G2 having positive refractive power, and third lens group G3 having positive refractive power arranged along an optical axis in order from the object side. When zooming from the wide-angle end to the telephoto end, at least the first lens group G1 and second lens group G2 move in such a way that a distance between the first lens group G1 and second lens group G2 decreases and a distance between the second lens group G2 and third lens group G3 increases. The zoom lens satisfies the following condition expressions: 0.80<(-f1)/(fw×ft)<1.20, 0.90<f2/fw<1.50, where f1 represents a focal length of the first lens group G1, fw represents a focal length of the zoom lens ZL at the wide-angle end, ft represents a focal length of the zoom lens ZL at the telephoto end, and f2 represents a focal length of the second lens group G2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens, an optical apparatus, and a zoom lens zooming method suitable for a still camera, a digital camera, and the like.

  In recent years, image pickup apparatuses (cameras) such as digital still cameras and digital video cameras using solid-state image pickup devices have been widely spread. In these photographing apparatuses, a zoom lens is generally used as an imaging lens. In order to provide a photographer with comfortable shooting, a compact zoom lens having a sufficient angle of view in the wide-angle end state and a large zoom ratio up to the telephoto end state is required. As an example of realizing the miniaturization of the zoom lens, there is Example 2 described in Patent Document 1.

JP 2011-154401 A

  Although the conventional zoom lens realizes an extremely small zoom lens, the angle of view at the wide-angle end state is slightly narrow and the zoom ratio is small.

  The present invention has been made in view of such problems, and has a zoom lens, an optical apparatus, and a zoom lens that are small in size, have a wider angle of view in the wide-angle end state, and have a high zoom ratio. An object is to provide a scaling method.

  In order to achieve such an object, a zoom lens according to the present invention includes a first lens group having a negative refractive power and a second lens having a positive refractive power, which are arranged in order from the object side along the optical axis. And a third lens group having a positive refractive power, and upon zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group decreases, At least the first lens group and the second lens group move so that the distance between the second lens group and the third lens group increases, and the following conditional expression is satisfied.

0.80 <(− f1) / (fw × ft) ^1/2 <1.20
0.90 <f2 / fw <1.50
However,
f1: the focal length of the first lens group,
fw: focal length of the zoom lens in the wide-angle end state
ft: focal length of the zoom lens in the telephoto end state;
f2: focal length of the second lens group.

  The zoom lens according to the present invention preferably satisfies the following conditional expression.

0.20 <f2 / f3 <0.40
However,
f3: focal length of the third lens group.

  The zoom lens according to the present invention preferably satisfies the following conditional expression.

  0.45 <fw / (-f1) <0.75

  The zoom lens according to the present invention preferably satisfies the following conditional expression.

  1.50 <ft / (− f1) <1.95

  The zoom lens according to the present invention preferably satisfies the following conditional expression.

1.75 <N
However,
N: The average value of the refractive indexes with respect to the d-line of the optical members of all the lenses included in the first lens group and the second lens group.

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

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

  The optical apparatus according to the present invention is equipped with any of the zoom lenses described above.

  The zoom lens zooming method according to the present invention includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, arranged in order from the object side along the optical axis, and a positive lens A zoom lens zooming method having a third lens group having refractive power and satisfying the following conditional expression, wherein the first lens group and the zoom lens are zoomed in from the wide-angle end state to the telephoto end state. At least the first lens group and the second lens group move so that the distance between the second lens group decreases and the distance between the second lens group and the third lens group increases.

0.80 <(− f1) / (fw × ft) ^1/2 <1.20
0.90 <f2 / fw <1.50
However,
f1: the focal length of the first lens group,
fw: focal length of the zoom lens in the wide-angle end state
ft: focal length of the zoom lens in the telephoto end state;
f2: focal length of the second lens group.

  According to the present invention, it is possible to provide a zoom lens, an optical apparatus, and a zoom lens zooming method that can ensure a wider angle of view in the wide-angle end state and have a high zoom ratio while being small.

It is a figure which shows the block diagram of the zoom lens which concerns on 1st Example of this embodiment, and the movement locus | trajectory of each lens group. (W), (M), and (T) indicate a wide-angle end state, an intermediate focal length state, and a telephoto end state, respectively. (A), (b), and (c) are graphs showing various aberrations of the zoom lens according to Example 1 of the present embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state at an imaging distance of infinity. is there. It is a figure which shows the block diagram of the zoom lens which concerns on 2nd Example of this embodiment, and the movement locus | trajectory of each lens group. (W), (M), and (T) indicate a wide-angle end state, an intermediate focal length state, and a telephoto end state, respectively. (A), (b), and (c) are aberration diagrams of the zoom lens according to the second example of the present embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state at an imaging distance of infinity. is there. It is a figure which shows the block diagram of the zoom lens which concerns on 3rd Example of this embodiment, and the movement locus | trajectory of each lens group. (W), (M), and (T) indicate a wide-angle end state, an intermediate focal length state, and a telephoto end state, respectively. (A), (b), and (c) are graphs showing various aberrations in the wide-angle end state, the intermediate focal length state, and the telephoto end state at an imaging distance of infinity of the zoom lens according to Example 3 of the present embodiment. is there. It is a figure explaining the digital camera (optical apparatus) carrying the zoom lens which concerns on this embodiment, (a) is a front view, (b) is a rear view. It is sectional drawing along the AA 'line of Fig.7 (a).

  Hereinafter, embodiments will be described with reference to the drawings.

  As shown in FIG. 1, the zoom lens ZL according to the present embodiment includes a first lens group G1 having negative refractive power, which is arranged in order from the object side along the optical axis, and a second lens group having positive refractive power. It has a lens group G2 and a third lens group G3 having a positive refractive power, and the distance between the first lens group G1 and the second lens group G2 is reduced upon zooming from the wide-angle end state to the telephoto end state. In addition, at least the first lens group G1 and the second lens group G2 are configured to move so that the distance between the second lens group G2 and the third lens group G3 increases.

  The zoom lens ZL is a negative leading zoom lens having three lens groups, negative, positive, and positive, arranged in order from the object side as described above. The second lens group G2 is a zoom unit and a master lens group. The first lens group G1 is a compensator group. The third lens group G3 optimizes the exit pupil position of the entire zoom lens system with respect to the image sensor, and corrects the remaining aberration that cannot be corrected by the first lens group G1 and the second lens group G2.

  In order to widen the zoom lens ZL having such a simple structure, to ensure a sufficient zoom ratio and to be compact, the power arrangement of each lens group, the refractive index of the optical material of each lens, the lens configuration, etc. Must be set appropriately.

  In the zoom lens ZL according to the present embodiment, it is preferable that the following conditional expression (1) is satisfied in order to reduce the size while widening the angle.

0.80 <(− f1) / (fw × ft) ^1/2 <1.20 (1)
However,
f1: Focal length of the first lens group G1
fw: focal length in the wide-angle end state of the zoom lens ZL,
ft: focal length of the zoom lens ZL in the telephoto end state.

  Zooming of the zoom lens ZL is performed by enlarging and reducing the image formed by the first lens group G1 with the subsequent lens group. When the specifications such as the focal length and zoom ratio of the entire zoom lens ZL system are determined, the magnification of the subsequent lens group is determined according to the focal length of the first lens group G1. Accordingly, the focal length of the first lens group G1 is an extremely important parameter in determining the characteristics of the entire zoom lens ZL. Conditional expression (1) defines an appropriate range of the focal length of the first lens group G1.

  If the lower limit value of conditional expression (1) is not reached, the magnification of the subsequent lens group becomes too high, so that the entire length of the zoom lens ZL becomes too long in the telephoto end state. Further, it is not preferable because spherical aberration in the telephoto end state is difficult to correct. If the upper limit of conditional expression (1) is exceeded, the magnification of the subsequent lens group becomes too low, so that the entire length of the zoom lens ZL becomes too long in the wide-angle end state, and the front lens diameter also becomes large. Further, it is not preferable because it is difficult to correct the upper coma aberration from the intermediate focal length state to the telephoto end state.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.85. In order to maximize the effects of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.90.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 1.15. In order to maximize the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 1.10.

  In the zoom lens ZL configured as described above, it is preferable that the following conditional expression (2) is satisfied.

0.90 <f2 / fw <1.50 (2)
However,
f2: focal length of the second lens group G2.

  Conditional expression (2) defines an appropriate range of the focal length of the second lens group G2. If the lower limit of conditional expression (2) is not reached, the refractive power of the second lens group G2 becomes too strong, and correction of spherical aberration occurring in the second lens group G2 becomes difficult, which is not preferable. Further, the Petzval sum is remarkably increased, and it becomes impossible to simultaneously correct the curvature of field and the astigmatic difference from the intermediate focal length state to the telephoto end state. Exceeding the upper limit of conditional expression (2) is not preferable because the Petzval sum becomes extremely small, and the field curvature and astigmatism cannot be corrected simultaneously from the intermediate focal length state to the telephoto end state.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.95. In order to maximize the effects of this embodiment, it is preferable to set the lower limit of conditional expression (2) to 1.00.

  In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 1.45. In order to maximize the effects of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 1.40.

  In the zoom lens ZL configured as described above, it is preferable that the following conditional expression (3) is satisfied.

0.20 <f2 / f3 <0.40 (3)
However,
f3: focal length of the third lens group G3.

  Conditional expression (3) defines an appropriate range for the ratio of the focal lengths of the second lens group G2 and the third lens group G3. If the lower limit of conditional expression (3) is not reached, the exit pupil position of the entire zoom lens ZL system is too close to the imaging surface, which is not preferable. In addition, it is difficult to correct field curvature in the wide-angle end state. Exceeding the upper limit of conditional expression (3) is not preferable because the Petzval sum is remarkably increased, which makes it difficult to correct curvature of field and astigmatism from the intermediate focal length state to the telephoto end state.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.24. In order to maximize the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.27.

  In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.39. In order to maximize the effects of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.37.

  In the zoom lens ZL configured as described above, it is preferable that the following conditional expression (4) is satisfied.

  0.45 <fw / (− f1) <0.75 (4)

  Conditional expression (4) defines an appropriate range for the ratio of the focal length of the entire zoom lens ZL system and the focal length of the first lens group G1 in the wide-angle end state. If the lower limit of conditional expression (4) is not reached, correction of coma aberration and field curvature in the wide-angle end state becomes difficult, which is not preferable. If the upper limit of conditional expression (4) is exceeded, the variation in spherical aberration due to zooming from the wide-angle end state to the telephoto end state becomes very large, and spherical aberration is corrected in both the wide-angle end state and the telephoto end state. Is not preferable because it becomes difficult.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.46. In order to maximize the effects of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.47.

  In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.70. In order to maximize the effects of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.65.

  In the zoom lens ZL configured as described above, it is preferable that the following conditional expression (5) is satisfied.

  1.50 <ft / (− f1) <1.95 (5)

  Conditional expression (5) defines an appropriate range for the ratio of the focal length of the entire zoom lens ZL to the focal length of the first lens group G1 in the telephoto end state. If the lower limit of conditional expression (5) is not reached, correction of coma aberration and field curvature in the wide-angle end state becomes difficult, which is not preferable. Exceeding the upper limit of conditional expression (5) is not preferable because it becomes difficult to correct spherical aberration in the telephoto end state.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (5) to 1.54. In order to maximize the effects of this embodiment, it is preferable to set the lower limit of conditional expression (5) to 1.58.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 1.90. In order to maximize the effects of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 1.85.

  In the zoom lens ZL configured as described above, it is preferable that the following conditional expression (6) is satisfied.

1.75 <N (6)
However,
N: The average value of the refractive indexes with respect to the d line of the optical members of all the lenses included in the first lens group G1 and the second lens group G2.

  Conditional expression (6) defines an appropriate range for the refractive indexes of the optical members of all the lenses included in the first lens group G1 and the second lens group G2. If the lower limit of conditional expression (6) is not reached, the radius of curvature of each lens included in the first lens group G1 and the second lens group G2 becomes too small, making it difficult to correct spherical aberration and coma aberration over the entire zoom range. Therefore, it is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 1.78. In order to maximize the effects of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 1.80.

  In the zoom lens ZL configured as described above, the first lens group G1 is composed of one negative lens and one positive lens arranged in order from the object side along the optical axis. preferable. This configuration is the minimum number of lenses that can correct the chromatic aberration, spherical aberration, coma aberration, and astigmatism of the first lens group G1, and the zoom lens ZL can be widened and miniaturized without degrading the optical performance. It is a necessary condition to do.

  In the zoom lens ZL configured as described above, the second lens group G2 is composed of two positive lenses and one negative lens arranged in order from the object side along the optical axis. preferable. With this configuration, it is possible to exert a converging effect on the light beam diverged by the first lens group G1 without causing excessive spherical aberration in the second lens group G2. In addition, it becomes possible to move the rear principal point of the second lens group G2 to the object side, and it becomes easy to ensure the distance between the first lens group G1 and the second lens group G2 in the telephoto end state.

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

  In the zoom lens ZL according to the present embodiment, any lens surface may be a diffractive surface. Further, any lens may be a gradient index lens (GRIN lens) or a plastic lens. Further, a lens group having a small refractive power may be added to the image side of the third lens group G3.

  In the zoom lens ZL according to the present embodiment, among the lens groups, one lens group or a part of the lenses may be moved in a direction substantially perpendicular to the optical axis. With this configuration, an image on the image plane can be moved, and a so-called anti-vibration lens can be realized.

  According to the present embodiment having the above-described configuration, the angle of view in the wide-angle end state is ensured wider (about 80 degrees) and has a high zoom ratio (about 3 to 4 times) while being extremely small. ), The zoom lens ZL can be realized.

  7 and 8 show a configuration of a digital still camera CAM (optical apparatus) including the above-described zoom lens ZL as a photographing lens. In this digital still camera CAM, when a power button (not shown) is pressed, a shutter (not shown) of the photographing lens (zoom lens ZL) is opened, and light from the subject (object) is condensed by the zoom lens ZL, and an image is displayed. An image is formed on an image sensor C (for example, a CCD or a CMOS) disposed on the surface I (see FIG. 1). The subject image formed on the image sensor C is displayed on the liquid crystal monitor M disposed behind the digital still camera CAM. The photographer determines the composition of the subject image while looking at the liquid crystal monitor M, and then depresses the release button B1 to photograph the subject image with the image sensor C, and records and saves it in a memory (not shown).

  The camera CAM is provided with an auxiliary light emitting unit EF for emitting auxiliary light when the subject is dark, a function button B2 used for setting various conditions of the digital still camera CAM, and the like. Here, a compact type camera in which the camera CAM and the zoom lens ZL are integrally formed is illustrated. However, as an optical device, a single lens reflex camera in which a lens barrel having the zoom lens ZL and a camera body main body can be attached and detached is used. good.

  According to the camera CAM having the above-described configuration, the zoom lens ZL according to the present embodiment is mounted as a photographing lens, thereby ensuring a wider angle of view in the wide-angle end state and having a high zoom ratio while being compact. A camera can be realized.

  Further, the zooming method of the zoom lens ZL according to the present embodiment includes a first lens group G1 having a negative refractive power and a second lens having a positive refractive power, which are arranged in order from the object side along the optical axis. In the zoom lens ZL having the group G2 and the third lens group G3 having positive refractive power and satisfying the following conditional expressions (1) and (2), as shown in FIG. During zooming from W) through the intermediate focal length state (M) to the telephoto end state (T), the distance between the first lens group G1 and the second lens group G2 decreases, and the second lens group G2 and the third lens group G3 At least the first lens group G1 and the second lens group G2 are moved so that the distance from the lens group G3 increases.

0.80 <(− f1) / (fw × ft) ^1/2 <1.20 (1)
0.90 <f2 / fw <1.50 (2)
However,
f1: Focal length of the first lens group G1
fw: focal length in the wide-angle end state of the zoom lens ZL,
ft: focal length of the zoom lens ZL in the telephoto end state,
f2: focal length of the second lens group G2.

  According to the above zooming method, in the zoom lens ZL, the field angle in the wide-angle end state is secured wider (about 80 degrees) and a high zooming ratio is achieved (3 to 4 times) while downsizing. Degree).

  Each example according to the present embodiment will be described with reference to the drawings. Tables 1 to 3 are shown below, but these are tables of specifications in the first to third examples.

  In addition, each reference code with respect to FIG. 1 according to the first embodiment is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, even if the same reference numerals as those in the drawings according to the other embodiments are given, they are not necessarily in the same configuration as the other embodiments.

  In each embodiment, the d-line (wavelength 587.5620 nm) and g-line (wavelength 435.8350 nm) are selected as the aberration characteristic calculation targets.

  In [Overall specifications] in the table, f represents the focal length of the entire zoom lens ZL system in each state, Fno represents the F number, 2ω represents the angle of view (unit: °), and Ymax represents the maximum image height.

  In [Lens Specifications] in the table, the surface number is the order of the optical surfaces from the object side along the light traveling direction, R is the radius of curvature of each optical surface, D is the next optical surface from each optical surface ( Or nd is the refractive index of the material of the optical member with respect to the d-line, and νd is the Abbe number based on the d-line of the material of the optical member. The object plane is the object plane, (variable) is the variable plane spacing, the curvature radius “∞” is the plane or aperture, (aperture S) is the aperture stop S, and the image plane is the image plane I. The refractive index of air “1.00000” is omitted. When the optical surface is an aspherical surface, the surface number is marked with *, and the column of curvature radius R indicates the paraxial curvature radius.

In [Aspherical data] in the table, the shape of the aspherical surface shown in [Lens specifications] is shown by the following equation (a). X (y) is the distance along the optical axis direction from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y, r is the radius of curvature of the reference sphere (paraxial radius of curvature), and κ is Ai represents the i-th aspherical coefficient. “E-n” indicates “× 10 ⁻ⁿ ”. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ .

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

  In [Variable interval data] in the table, each variable interval Di (variable interval between the i-th surface and the (i + 1) -th surface) in each of the wide-angle end state, the intermediate focal length state, and the telephoto end state, TL is the zoom lens ZL. The full length, BF, indicates the back focus (distance from the image side surface of the optical member arranged closest to the image side to the paraxial image surface).

  In [Lens Group Data] in the table, G represents the group number, the first group surface represents the surface number closest to the object in each group, and the group focal length represents the focal length of each group.

  In [Conditional Expression] in the table, values corresponding to the conditional expressions (1) to (6) are shown.

  Hereinafter, in all the specification values, “mm” is generally used for the focal length f, curvature radius R, surface distance D, and other lengths, etc. unless otherwise specified, but the optical system is proportionally enlarged. Alternatively, the same optical performance can be obtained even by proportional reduction, and the present invention is not limited to this. Further, the unit is not limited to “mm”, and other appropriate units can be used.

  The description of the table so far is common to all the embodiments, and the description below is omitted.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. As shown in FIG. 1, the zoom lens ZL (ZL1) according to the first example includes a first lens group G1 having negative refractive power arranged in order from the object side along the optical axis, and a positive refractive power. A second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a filter group FL.

  In zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. As described above, the first lens group G1 and the second lens group G2 move. The third lens group G3 is fixed and does not move during zooming.

  The first lens group G1 includes a negative lens L11 and a positive lens L12 arranged in order from the object side along the optical axis. The object-side and image-side lens surfaces of the negative lens L11 and the image-side lens surface of the positive lens L12 are both aspherical surfaces.

  The second lens group G2 includes a positive lens L21 and a cemented lens of a positive lens L22 and a negative lens L23 arranged in order from the object side along the optical axis. Both the object-side and image-side lens surfaces of the positive lens L21 are aspherical surfaces.

  The third lens group G3 includes only one positive lens L31. The lens surface on the image side of the positive lens L31 is an aspherical surface.

  A diaphragm S for determining an F-number is disposed between the first lens group G1 and the second lens group G2, and has the same trajectory as the second lens group G2 upon zooming from the wide-angle end state to the telephoto end state. Move with.

  The filter group FL is composed of a low-pass filter, an infrared cut filter, and the like for cutting a spatial frequency equal to or higher than the limit resolution of a solid-state imaging device (for example, CCD or CMOS) disposed on the image plane I.

  Table 1 below shows the values of each item in the first example. Surface numbers 1 to 14 in Table 1 correspond to the optical surfaces having the curvature radii R1 to R14 shown in FIG. In the first embodiment, the first surface, the second surface, the fourth surface, the sixth surface, the seventh surface, and the twelfth surface are aspherical surfaces.

(Table 1)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f 5.15 8.70 14.70
Fno 3.34 4.49 6.44
2ω 80.45 51.65 31.39
Ymax 3.50 3.90 3.90

[Lens specifications]
Surface number R D nd νd
Object ∞
* 1 -19.1765 0.4500 1.88202 37.23
* 2 5.7448 0.5200
3 6.0802 1.2500 1.92286 20.88
* 4 11.5477 D4 (variable)
5 ∞ -0.0500 (Fno decision surface)
* 6 5.8378 1.1500 1.59201 67.05
* 7 -6.9426 0.1500
8 3.4770 1.1000 1.88300 40.66
9 391.4576 0.4000 1.95000 29.37
10 2.4300 D10 (variable)
11 -1000.0000 1.8000 1.53153 55.95
* 12 -9.5350 D12 (variable)
13 ∞ 0.5000 1.51680 63.88
14 ∞ BF
Image plane ∞

[Aspherical data]
(First side)
κ = 1.0000, A4 = 2.74116E-03, A6 = -1.23404E-04, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Second side)
κ = -0.0890, A4 = 4.55493E-03, A6 = 3.18602E-04, A8 = -1.25219E-06, A10 = -3.04823E-06
(Fourth surface)
κ = 1.0000, A4 = -5.46977E-04, A6 = -3.42618E-04, A8 = 4.40386E-05, A10 = -1.48556E-06
(Sixth surface)
κ = 1.0000, A4 = -1.73166E-03, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Seventh side)
κ = 0.0281, A4 = -1.28778E-04, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Twelfth surface)
κ = -8.8758, A4 = -1.11069E-03, A6 = 1.29644E-05, A8 = -1.71727E-07, A10 = 0.00000E + 00

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state
Infinity infinity infinity infinity
f 5.15 8.70 14.70
D4 4.9573 2.0187 0.2787
D10 2.5060 5.3490 10.1541
D12 2.0682 2.0682 2.0682
BF 0.6000 0.6000 0.6000
TL 17.4015 17.3059 20.3710

[Lens group data]
Group number Group first surface Group focal length G1 1 -8.15
G2 6 5.45
G3 11 18.10

[Conditional expression]
Conditional expression (1) (−f1) / (fw × ft) ^1/2 = 0.9367
Conditional expression (2) f2 / fw = 1.0583
Conditional expression (3) f2 / f3 = 0.2962
Conditional expression (4) fw / (− f1) = 0.6319
Conditional expression (5) ft / (− f1) = 1.8037
Conditional expression (6) N = 1.8460

  From Table 1, it can be seen that the zoom lens ZL1 according to the present example satisfies the conditional expressions (1) to (6).

  FIG. 2 is a diagram illustrating various aberrations (spherical aberration diagram, astigmatism diagram, distortion diagram, coma diagram, and chromatic aberration diagram of magnification) at the time of focusing on infinity in the zoom lens ZL1 according to the first example. ) Shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows the telephoto end state.

  In each aberration diagram, FNO is an F number, Y is an image height, and A is a half field angle (unit: °) with respect to each image height. d indicates the d-line, and g indicates the aberration at the g-line. Those not described indicate aberrations at the d-line. In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, the solid line indicates meridional coma aberration, the dotted line indicates sagittal coma aberration, the dotted line on the right side from the origin indicates the sagittal coma aberration generated in the meridional direction with respect to the d line, and the dotted line on the left side from the origin indicates the d line. The sagittal coma aberration generated in the sagittal direction is shown respectively.

  The description regarding these aberration diagrams is the same in other examples, and the description thereof is omitted.

  As is apparent from the respective aberration diagrams, in the first 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 optical performance is obtained.

(Second embodiment)
A second embodiment will be described with reference to FIGS. 3 and 4 and Table 2. FIG. As shown in FIG. 3, the zoom lens ZL (ZL2) according to the second example includes a first lens group G1 having negative refractive power arranged in order from the object side along the optical axis, and a positive refractive power. A second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a filter group FL.

  In zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. As described above, the first lens group G1 and the second lens group G2 move. The third lens group G3 is fixed and does not move during zooming.

  The first lens group G1 includes a negative lens L11 and a positive lens L12 arranged in order from the object side along the optical axis. The object-side and image-side lens surfaces of the negative lens L11 and the image-side lens surface of the positive lens L12 are both aspherical surfaces.

  The second lens group G2 includes a positive lens L21 and a cemented lens of a positive lens L22 and a negative lens L23 arranged in order from the object side along the optical axis. Both the object-side and image-side lens surfaces of the positive lens L21 are aspherical surfaces.

  The third lens group G3 includes only one positive lens L31. The lens surface on the image side of the positive lens L31 is an aspherical surface.

  A diaphragm S for determining an F-number is disposed between the first lens group G1 and the second lens group G2, and has the same trajectory as the second lens group G2 upon zooming from the wide-angle end state to the telephoto end state. Move with.

  The filter group FL is composed of a low-pass filter, an infrared cut filter, and the like for cutting a spatial frequency higher than the limit resolution of a solid-state imaging device (for example, CCD or CMOS) disposed on the image plane I. .

  Table 2 below shows the values of each item in the second embodiment. Surface numbers 1 to 14 in Table 2 correspond to the optical surfaces having the curvature radii R1 to R14 shown in FIG. In the second embodiment, the first surface, the second surface, the fourth surface, the sixth surface, the seventh surface, and the twelfth surface are aspherical surfaces.

(Table 2)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f 5.15 8.70 14.70
Fno 3.52 4.68 6.64
2ω 79.99 51.36 31.13
Ymax 3.50 3.90 3.90

[Lens specifications]
Surface number R D nd νd
Object ∞
* 1 435.3026 0.4500 1.85135 40.10
* 2 5.0647 0.8000
3 8.6549 1.2500 1.92286 20.88
* 4 16.9171 D4 (variable)
5 ∞ -0.2500 (Fno decision plane)
* 6 4.6737 1.2500 1.61881 63.86
* 7 -9.4864 0.1500
8 4.1171 1.1000 1.88300 40.66
9 105.3274 0.4000 1.95000 29.37
10 2.5875 D10 (variable)
11 -1000.0000 1.7500 1.53153 55.95
* 12 -10.0042 D12 (variable)
13 ∞ 0.5000 1.51680 63.88
14 ∞ BF
Image plane ∞

[Aspherical data]
(First side)
κ = 1.0000, A4 = -1.12000E-03, A6 = 6.71000E-05, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Second side)
κ = 1.0000, A4 = -6.94000E-05, A6 = 1.62000E-04, A8 = -2.24000E-05, A10 = 2.82000E-06
(Fourth surface)
κ = 1.0000, A4 = -1.34000E-03, A6 = 7.35000E-05, A8 = -8.37000E-06, A10 = -2.02000E-07
(Sixth surface)
κ = 1.2387, A4 = -1.19000E-03, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Seventh side)
κ = -11.3351, A4 = 0.00000E + 00, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Twelfth surface)
κ = 0.0561, A4 = -8.79000E-06, A6 = -9.31000E-06, A8 = 7.10000E-06, A10 = 0.00000E + 00

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state
Infinity infinity infinity infinity
f 5.15 8.70 14.70
D4 6.2273 2.5993 0.4510
D10 2.5131 5.2577 9.8966
D12 2.1884 2.1884 2.1884
BF 0.6000 0.6000 0.6000
TL 18.9288 18.0454 20.5360

[Lens group data]
Group number Group first surface Group focal length G1 1 -9.20
G2 6 5.95
G3 11 19.00

[Conditional expression]
Conditional expression (1) (−f1) / (fw × ft) ^1/2 = 1.0763
Conditional expression (2) f2 / fw = 1.1972
Conditional expression (3) f2 / f3 = 0.3132
Conditional expression (4) fw / (-f1) = 0.5402
Conditional expression (5) ft / (− f1) = 1.5978
Conditional expression (6) N = 1.8452

  From Table 2, it can be seen that the zoom lens ZL2 according to the present example satisfies the conditional expressions (1) to (6).

  FIG. 4 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, distortion diagram, coma diagram, and lateral chromatic aberration diagram) at the time of focusing on infinity in the zoom lens ZL2 according to Example 2. ) Shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows 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 optical performance is obtained.

(Third embodiment)
A third embodiment will be described with reference to FIGS. As shown in FIG. 5, the zoom lens ZL (ZL3) according to the third example includes a first lens group G1 having negative refractive power arranged in order from the object side along the optical axis, and positive refractive power. A second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a filter group FL.

  In zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2 decreases, and the distance between the second lens group G2 and the third lens group G3 increases. As described above, the first lens group G1 and the second lens group G2 move. The third lens group G3 is fixed and does not move during zooming.

  The first lens group G1 includes a negative lens L11 and a positive lens L12 arranged in order from the object side along the optical axis. The object side and image side lens surfaces of the negative lens L11 and the object side and image side lens surfaces of the positive lens L12 are both aspherical surfaces.

  The second lens group G2 includes a positive lens L21 and a cemented lens of a positive lens L22 and a negative lens L23 arranged in order from the object side along the optical axis. Both the object-side and image-side lens surfaces of the positive lens L21 are aspherical surfaces.

  The third lens group G3 includes only one positive lens L31. The lens surface on the image side of the positive lens L31 is an aspherical surface.

  A diaphragm S for determining an F-number is disposed between the first lens group G1 and the second lens group G2, and has the same trajectory as the second lens group G2 upon zooming from the wide-angle end state to the telephoto end state. Move with.

  The filter group FL is composed of a low-pass filter, an infrared cut filter, and the like for cutting a spatial frequency higher than the limit resolution of a solid-state imaging device (for example, CCD or CMOS) disposed on the image plane I. .

  Table 3 below shows values of various specifications in the third example. Surface numbers 1 to 14 in Table 3 correspond to the optical surfaces having the curvature radii R1 to R14 shown in FIG. In the third embodiment, the first surface, the second surface, the third surface, the fourth surface, the sixth surface, the seventh surface, and the twelfth surface are aspherical surfaces.

(Table 3)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f 5.15 10.00 19.40
Fno 3.07 4.34 6.82
2ω 80.16 44.99 23.91
Ymax 3.50 3.90 3.90

[Lens specifications]
Surface number R D nd νd
Object ∞
* 1 -33.34557 0.4500 1.88202 37.23
* 2 6.20522 0.8300
* 3 8.30745 1.3500 1.92286 20.88
* 4 21.49237 D4 (variable)
5 ∞ -0.2500 (Fno decision plane)
* 6 4.84551 1.3500 1.62000 63.90
* 7 -12.05761 0.1500
8 4.43946 1.2000 1.80000 46.60
9 -1000.00000 0.4000 1.90000 31.30
10 2.73022 D1000 (variable)
11 -1000.00000 1.6500 1.53153 55.95
* 12 -10.78509 D12 (variable)
13 ∞ 0.5000 1.51680 63.88
14 ∞ BF
Image plane ∞

[Aspherical data]
(First side)
κ = 1.0000, A4 = 5.48370E-04, A6 = -9.24590E-06, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Second side)
κ = 0.5186, A4 = 3.78770E-04, A6 = 1.00530E-04, A8 = -4.44450E-06, A10 = 1.28750E-07
(Third side)
κ = -3.0000, A4 = 0.00000E + 00, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Fourth surface)
κ = 1.0000, A4 = -7.52260E-04, A6 = -4.18450E-05, A8 = 3.41160E-06, A10 = -1.44570E-07
(Sixth surface)
κ = -0.0004, A4 = 8.58050E-05, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Seventh side)
κ = -9.6206, A4 = 0.00000E + 00, A6 = 0.00000E + 00, A8 = 0.00000E + 00, A10 = 0.00000E + 00
(Twelfth surface)
κ = -2.8761, A4 = -1.81640E-04, A6 = -1.27780E-05, A8 = 3.01010E-07, A10 = 0.00000E + 00

[Variable interval data]
Wide-angle end state Intermediate focal length state Telephoto end state
Infinity infinity infinity infinity
f 5.15 10.00 19.40
D4 9.7400 3.6057 0.4496
D10 3.2331 7.0716 14.5112
D12 2.3621 2.3621 2.3621
BF 0.6000 0.6000 0.6000
TL 23.5652 21.2694 25.5529

[Lens group data]
Group number Group first surface Group focal length G1 1 -10.80
G2 6 7.18
G3 11 20.50

[Conditional expression]
Conditional expression (1) (−f1) / (fw × ft) ^1/2 = 1.0805
Conditional expression (2) f2 / fw = 1.3942
Conditional expression (3) f2 / f3 = 0.3132
Conditional expression (4) fw / (− f1) = 0.4769
Conditional expression (5) ft / (− f1) = 1.7963
Conditional expression (6) N = 1.8250

  From Table 3, it can be seen that the zoom lens ZL3 according to the present example satisfies the conditional expressions (1) to (6).

  FIG. 6 is a diagram of various aberrations (spherical aberration diagram, astigmatism diagram, distortion diagram, coma diagram, and chromatic aberration diagram of magnification) at the time of focusing on infinity in the zoom lens ZL3 according to Example 3, (a ) Shows the wide-angle end state, (b) shows the intermediate focal length state, and (c) shows the telephoto end state.

  As is apparent from each aberration diagram, in the third 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 the optical performance is excellent.

  As described above, according to the first to third embodiments, the angle of view in the wide-angle end state is as wide as about 80 degrees while being small, and has a high zoom ratio of about 3 to 4 times. A zoom lens can be realized.

  In order to make the present invention easy to understand, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

ZL (ZL1 to ZL3) Zoom lens CAM Digital still camera (optical equipment)
G1 First lens group G2 Second lens group G3 Third lens group FL filter group S Aperture I Image surface

Claims (9)

A first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, which are arranged in order from the object side along the optical axis. ,
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group is decreased, and the distance between the second lens group and the third lens group is increased. , At least the first lens group and the second lens group move,
A zoom lens satisfying the following conditional expression:
0.80 <(− f1) / (fw × ft) ^1/2 <1.20
0.90 <f2 / fw <1.50
However,
f1: the focal length of the first lens group,
fw: focal length of the zoom lens in the wide-angle end state
ft: focal length of the zoom lens in the telephoto end state;
f2: focal length of the second lens group. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.20 <f2 / f3 <0.40
However,
f3: focal length of the third lens group. The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
0.45 <fw / (-f1) <0.75 The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.50 <ft / (− f1) <1.95 The zoom lens according to claim 1, wherein the following conditional expression is satisfied.
1.75 <N
However,
N: The average value of the refractive indexes with respect to the d-line of the optical members of all the lenses included in the first lens group and the second lens group.   The first lens group includes one negative lens and one positive lens arranged in order from the object side along the optical axis. The described zoom lens.   The said 2nd lens group consists of two positive lenses and one negative lens which were arranged in order from the object side along the optical axis. The described zoom lens.   An optical apparatus comprising the zoom lens according to any one of claims 1 to 7. A first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power, which are arranged in order from the object side along the optical axis. A zoom lens zooming method that satisfies the following conditional expression:
During zooming from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group is decreased, and the distance between the second lens group and the third lens group is increased. A zoom lens zooming method, wherein at least the first lens group and the second lens group move.
0.80 <(− f1) / (fw × ft) ^1/2 <1.20
0.90 <f2 / fw <1.50
However,
f1: the focal length of the first lens group,
fw: focal length of the zoom lens in the wide-angle end state
ft: focal length of the zoom lens in the telephoto end state;
f2: focal length of the second lens group.

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