JP4194876B2 - Zoom lens - Google Patents

Description

【００６３】
ただし、ｒは近軸曲率半径、Ｋは円錐係数、Ａ₄，Ａ₆，Ａ₈，Ａ₁₀はそれぞれ４次，６次，８次，１０次の非球面係数である。
【００６４】
以上説明したように、本発明によれば、１０倍程度の高変倍比を有しながらも、全長が短く、前玉径も小さい広画角のズームレンズを提供することができる。また、このズームレンズは全変倍域において結像性能が安定している。特に、望遠端において１ｍ程度の近距離にピントを合わせたときの像面湾曲や色収差の変動が小さくなっている。したがって、本発明のズームレンズは、小型で画素数の多い撮像素子にも十分対応可能であり、特に近年コンパクト化が著しいデジタルスチルカメラやビデオカメラに最適である。
【００６５】
以上、本発明の一実施形態を図面に沿って説明した。しかしながら本発明はこの実施の形態に示した事項に限定されず、特許請求の範囲の記載に基づいてその変更、改良等が可能である。
【００６６】
【発明の効果】
上述のように、本発明によれば、十分なコンパクト化が達成されると共に、高変倍比と共に高い光学性能を備えたズームレンズを提供することができる。このズームレンズは、特に小型で画素数の多い撮像素子を搭載したコンパクトなデジタルスチルカメラやビデオカメラに最適なものとなる。
【図面の簡単な説明】
【図１】 実施の形態１にかかるズームレンズの構成を示す光軸に沿う断面図である。
【図２】 実施の形態１にかかるズームレンズの広角端（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図３】 実施の形態１にかかるズームレンズの広角端（無限遠）におけるコマ収差を示す図である。
【図４】 実施の形態１にかかるズームレンズの中間倍率（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図５】 実施の形態１にかかるズームレンズの中間倍率（無限遠）におけるコマ収差を示す図である。
【図６】 実施の形態１にかかるズームレンズの望遠端（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図７】 実施の形態１にかかるズームレンズの望遠端（無限遠）におけるコマ収差を示す図である。
【図８】 実施の形態１にかかるズームレンズの望遠端（物体距離９０ｃｍ）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図９】 実施の形態１にかかるズームレンズの望遠端（物体距離９０ｃｍ）におけるコマ収差を示す図である。
【図１０】 実施の形態２にかかるズームレンズの構成を示す光軸に沿う断面図である。
【図１１】 実施の形態２にかかるズームレンズの広角端（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図１２】 実施の形態２にかかるズームレンズの広角端（無限遠）におけるコマ収差を示す図である。
【図１３】 実施の形態２にかかるズームレンズの中間倍率（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図１４】 実施の形態２にかかるズームレンズの中間倍率（無限遠）におけるコマ収差を示す図である。
【図１５】 実施の形態２にかかるズームレンズの望遠端（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図１６】 実施の形態２にかかるズームレンズの望遠端（無限遠）におけるコマ収差を示す図である。
【図１７】 実施の形態２にかかるズームレンズの望遠端（物体距離９０ｃｍ）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図１８】 実施の形態２にかかるズームレンズの望遠端（物体距離９０ｃｍ）におけるコマ収差を示す図である。
【図１９】 実施の形態３にかかるズームレンズの構成を示す光軸に沿う断面図である。
【図２０】 実施の形態３にかかるズームレンズの広角端（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図２１】 実施の形態３にかかるズームレンズの広角端（無限遠）におけるコマ収差を示す図である。
【図２２】 実施の形態３にかかるズームレンズの中間倍率（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図２３】 実施の形態３にかかるズームレンズの中間倍率（無限遠）におけるコマ収差を示す図である。
【図２４】 実施の形態３にかかるズームレンズの望遠端（無限遠）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図２５】 実施の形態３にかかるズームレンズの望遠端（無限遠）におけるコマ収差を示す図である。
【図２６】 実施の形態３にかかるズームレンズの望遠端（物体距離８０ｃｍ）における球面収差、像面湾曲、歪曲収差、および倍率の色収差を示す図である。
【図２７】 実施の形態３にかかるズームレンズの望遠端（物体距離８０ｃｍ）におけるコマ収差を示す図である。
【符号の説明】
１１，２１，３１ 第１レンズ群
１２，２２，３２ 第２レンズ群
１３，２３，３３ 第３レンズ群
１４，２４，３４ 第４レンズ群
１５，２５，３５ 絞り
１２１，２２１，３２１ 第１レンズ
１２２，２２２，３２２ 第２レンズ
１２３，２２３，３２３ 第３レンズ
１２４，２２４，３２４ 第４レンズ
ｅ ｅ線
ｄ ｄ線
ｇ ｇ線
Ｓ サジタル像面
Ｔ メリディオナル像面[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a zoom lens suitable for a high-quality digital still camera or video camera.
[0002]
[Prior art]
  In recent years, digital still cameras and video cameras have been widely used, and higher image quality is required. In particular, digital still cameras are equipped with an image pickup device having a large number of pixels. For this reason, there is a demand for a photographic lens, particularly a zoom lens, which has excellent imaging performance. In particular, a digital still camera equipped with a single-lens reflex finder requires a long back focus zoom lens. Therefore, various zoom lenses that can be used for such digital still cameras and video cameras have been proposed (see, for example, Patent Documents 1 and 2). A zoom lens having a four-group configuration is also disclosed in Patent Documents 3 to 5 below.
[0003]
[Patent Document 1]
          Japanese Patent Laid-Open No. 11-23967
[Patent Document 2]
          Japanese Patent Laid-Open No. 5-60974
[Patent Document 3]
          JP 2001-33695 A
[Patent Document 4]
          JP 2002-169087 A
[Patent Document 5]
          Japanese Patent No. 3387687
[0004]
[Problems to be solved by the invention]
  The zoom lens described in Patent Document 1 can achieve a zoom ratio of about 2.5 times and has a field angle of about 60 ° at the wide-angle end. It is possible to correspond to. However, this zoom lens configuration cannot achieve a zoom ratio of 3 times or more. It is an unsuitable lens for recent digital still cameras that require high-magnification images with the advent of image sensors that can achieve high image quality.
[0005]
  In addition, the zoom lens described in Patent Document 2 is a compact lens having 10 or less lenses and a relatively high zoom ratio. This zoom lens includes an aspherical lens having a strong positive refractive power in the third lens group and a negative meniscus lens having a concave surface facing the image side, and has a short overall length. For this reason, the incident angle of the light beam emitted from the third lens group becomes tight, and the aberration fluctuation during focus adjustment during close-up photography becomes severe. Therefore, when this zoom lens is used in a digital still camera equipped with an image pickup device having a large number of pixels, an image forming performance sufficient for an image pickup device having a large number of pixels cannot be obtained.
[0006]
  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a zoom lens that has a high zoom ratio of about 10 times but has excellent imaging performance even though it is small. Is to provide.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, a zoom lens according to a first aspect of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a positive lens group. A third lens group having a refractive power and a fourth lens group having a positive refractive power are arranged and configured;
  A zoom lens, wherein zooming is performed by moving the second lens and the fourth lens group in a direction along an optical axis, and satisfies the following conditional expression:
      1.2 <| f2 / fw | <1.4
      6.2 <f1 / fw <7.2
      5.5 <f3 / fw <7.2
      2.6 <f4 / fw <3.1
  Where f2 is the focal length of the second lens group,f1 is the focal length of the first lens group, f3 is the focal length of the third lens group, f4 is the focal length of the fourth lens group,fw represents the focal length at the short focal end of the zoom lens.
[0008]
  According to the first aspect of the present invention, it is possible to provide a compact zoom lens that is suitable for high-quality digital still cameras and video cameras, has excellent imaging performance, and has a wide angle of view and a high zoom ratio. .
[0015]
  Also,Claim 2The zoom lensClaim 1The first lens group includes at least two or more convex lenses, and when the average value of the Abbe numbers of the convex lenses included in the first lens group is ν1, the following conditional expression is satisfied: It is characterized by satisfaction.
      58 ≦ ν1 <65
[0016]
  thisClaim 2According to the invention described inClaim 1It is possible to provide a zoom lens having imaging performance that is even better than the invention described in (1).
[0017]
  Also,Claim 3The zoom lensClaim 1 or 2The third lens group includes at least one convex lens and at least one concave lens, and an aspherical surface is formed on at least one of the lenses included in the third lens group. It is characterized by being.
[0018]
  thisClaim 3According to the invention described in (1), it is possible to correct aberrations satisfactorily.
[0019]
  Also,Claim 4The zoom lensClaims 1-3In the invention described in any one of the above, at least one of the lenses included in the fourth lens group is formed with an aspherical surface.
[0020]
  thisClaim 4According to the invention described in (4), it is possible to perform better aberration correction.
[0021]
  Also,Claim 5The zoom lensClaims 1-4In the invention according to any one of the above, in the second lens group, a concave lens first lens, a concave lens second lens, a concave lens third lens, and a convex lens fourth lens are arranged in this order from the object side. The third lens and the fourth lens are cemented.
[0022]
  thisClaim 5According to the invention described in (4), a member such as a spacer for fixing the third lens and the fourth lens becomes unnecessary, and adjustment of the coaxiality of the lens becomes easy, so that the zoom lens manufacturing process is simplified. This can reduce the cost.
[0023]
  Also,Claim 6The zoom lensIn the invention of claim 1,The first lens group includes at least two convex lenses, and the second lens group includes, in order from the object side, a first lens that is a concave lens, a second lens that is a concave lens, a third lens that is a concave lens, and a fourth lens that is a convex lens. The third lens group is formed by bonding the third lens and the fourth lens, and the third lens group includes at least one or more convex lenses and at least one or more concave lenses, At least one of the lenses included in the three lens groups has an aspheric surface, and the fourth lens group has an aspheric surface formed on at least one of the lenses included in the fourth lens group. When changing the magnification from the short focal point to the long focal point by moving the second lens group and the fourth lens group in the direction along the optical axis, the fourth lens group is moved to the object side. After moving to , So as to move toward the image side, and, when performing the focusing is characterized by moving in the direction along the fourth lens unit in the optical axis.
[0024]
  thisClaim 6Since the fourth lens group is moved to the image side after moving to the object side during zooming from the short focal end to the long focal end, the front lens diameter of the zoom lens is Can be reduced, and aberration correction is advantageous, and a wide angle can be achieved. In addition, since focusing is performed by moving the fourth lens group in the direction along the optical axis, it is possible to prevent enlargement of the front lens diameter and to prevent deterioration of optical performance during focusing.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
  The zoom lens of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens power. A fourth lens group having a refractive power of is arranged. At the time of zooming, the second lens and the fourth lens group move in a direction along the optical axis.
[0026]
  An object of the present invention is to provide a zoom lens that can be used in a compact digital still camera, video camera, or the like. For this purpose, it is necessary not only to make the lens compact, but also to have high optical performance that does not impair the performance of a small-sized image sensor with a large number of pixels. Therefore, first, it is preferable that the zoom lens of the present invention satisfies the following conditional expression when the focal length of the second lens group is f2 and the focal length at the short focal point of the zoom lens is fw.
      1.2 <| f2 / fw | <1.4 (1)
[0027]
  Conditional expression (1) is an expression for determining the ratio between the focal length of the second lens group and the focal length at the short focal end of the zoom lens of the present invention. In conditional expression (1), if the value of | f2 / fw | is 1.4 or more, the amount of movement of the second lens group at the time of zooming increases, so the total length of the zoom lens must be increased. Zoom lens cannot be made compact. On the other hand, when the value of | f2 / fw | is 1.2 or less, it becomes an advantageous condition for making the zoom lens compact, but the field curvature and distortion occurring in the short focal range of the zoom lens become remarkable. Therefore, it is not preferable.
[0028]
  Furthermore, in the zoom lens of the present invention, it is preferable that the following conditional expression is satisfied when the focal length of the first lens group is f1.
      6.2 <f1 / fw <7.2 (2)
[0029]
  Conditional expression (2) is an expression for determining the ratio between the focal length of the first lens group and the focal length at the short focal end of the zoom lens of the present invention. In conditional expression (2), if the value of f1 / fw is 7.2 or more, the total length of the zoom lens becomes long, and sufficient compactness cannot be achieved. On the other hand, if the value of f1 / fw is 6.2 or less, spherical aberration and chromatic aberration that occur in the long focal range of the zoom lens become significant, which is not preferable.
[0030]
  Furthermore, in the zoom lens according to the present invention, it is preferable that the following conditional expression is satisfied when the focal length of the third lens group is f3.
      5.5 <f3 / fw <7.2 (3)
[0031]
  Conditional expression (3) is an expression for determining the ratio between the focal length of the third lens group and the focal length at the short focal end of the zoom lens of the present invention. In conditional expression (3), if the value of f3 / fw is 7.2 or more, the back focus of the zoom lens becomes long, and the zoom lens cannot be sufficiently compact. On the other hand, if the value of f3 / fw is 5.5 or less, the occurrence of spherical aberration becomes significant, which is not preferable.
[0032]
  Furthermore, in the zoom lens according to the present invention, it is preferable that the following conditional expression is satisfied when the focal length of the fourth lens group is f4.
      2.6 <f4 / fw <3.1 (4)
[0033]
  Conditional expression (4) is an expression for determining the ratio between the focal length of the fourth lens group and the focal length at the short focal end of the zoom lens of the present invention. In conditional expression (4), if the value of f4 / fw is 3.1 or more, the overall length of the zoom lens becomes long, and compactness cannot be achieved. On the other hand, when the value of f4 / fw is 2.6 or less, the back focus of the zoom lens becomes too short, and a space for arranging an optical member such as a low-pass filter cannot be secured. In addition, the occurrence of spherical aberration becomes remarkable in the short focal range, which is not preferable.
[0034]
  Furthermore, in the zoom lens according to the present invention, the first lens group includes at least two convex lenses, and when the average value of the Abbe number of the convex lenses included in the first lens group is ν1, the following condition is satisfied. It is preferable to satisfy the formula.
      58 ≦ ν1 <65 (5)
[0035]
  In this conditional expression (5), when the value of ν1 is 65 or more, chromatic aberration can be corrected. However, particularly in correcting chromatic aberration occurring in the long focal range, a cost problem arises. On the other hand, when the value of ν1 is less than 58, it becomes difficult to correct chromatic aberration well.
[0036]
  The zoom lens of the present invention moves the second lens and the fourth lens group in the direction along the optical axis at the time of zooming. In particular, at the time of zooming from the short focus end to the long focus end, the fourth lens group is moved to the image side after being moved to the object side, so that the front lens diameter of the zoom lens can be reduced. Also, by doing so, it is advantageous in correcting aberrations, and a wide angle can be achieved. In addition, the variation of spherical aberration with respect to the change in the object distance of the entire lens system is stable, so that sufficient imaging performance can be obtained during close-up photography, and the total length of the third lens group is not increased, so that sufficient back focus can be obtained. It is done. Furthermore, by setting the focal length of the first lens group to be relatively long, and by imparting a relatively large zooming burden to the third lens group and the fourth lens group, it is possible to achieve high zooming, In particular, optical performance required for a digital still camera, a video camera, or the like on which a solid-state imaging device such as a CCD having 3 million pixels or more is mounted can be obtained.
[0037]
  Further, when focusing is performed by moving the first lens unit to the object side, there arises a problem that the front lens diameter of the zoom lens is increased. Therefore, in the zoom lens of the present invention, focusing is performed by moving the fourth lens group in the direction along the optical axis, so that an increase in the front lens diameter is prevented and optical performance is deteriorated during focusing. Can be prevented.
[0038]
  In the zoom lens according to the present invention, the third lens group includes at least one convex lens and at least one concave lens. In addition, an aspherical surface is formed on at least one of the lenses included in the third lens group. Further, at least one of the lenses included in the fourth lens group has an aspheric surface. By doing so, it is possible to satisfactorily correct aberrations from the wide-angle end to the telephoto end.
[0039]
  In the zoom lens according to the present invention, the second lens group includes, in order from the object side, a first lens that is a concave lens, a second lens that is a concave lens, a third lens that is a concave lens, and a fourth lens that is a convex lens. The third lens and the fourth lens are cemented. By joining the third lens and the fourth lens, a member such as a spacer for fixing the third lens and the fourth lens becomes unnecessary. In addition, the coaxiality of the lens can be easily adjusted. Accordingly, the manufacturing process of the zoom lens can be simplified and the cost can be reduced.
[0040]
  Since the zoom lens according to the present invention is configured as described above, it is most suitable for a digital still camera or a video camera in which a high image quality is required, and particularly a solid-state imaging device such as a CCD having 3 million pixels or more is mounted. It becomes.
[0041]
  Embodiments of the present invention will be described below.
[0042]
(Embodiment 1)
  FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the present embodiment. 1A shows a state at the wide-angle end, FIG. 1B shows an intermediate magnification, and FIG. 1C shows a state at the telephoto end. In this zoom lens, in order from an object side (not shown), a first lens group 11 having a positive refractive power, a second lens group 12 having a negative refractive power, and a third lens group 13 having a positive refractive power. , And a fourth lens group 14 having a positive refractive power is arranged. The first lens group 11 includes two convex lenses. The second lens group 12 includes a first lens 121 that is a concave lens, a second lens 122 that is a concave lens, a third lens 123 that is a concave lens, and a fourth lens 124 that is a convex lens. The lens 124 is cemented. The third lens group 13 includes one convex lens and one concave lens. A diaphragm 15 is disposed between the second lens group 12 and the third lens group 13.
[0043]
  Various numerical data related to the zoom lens according to the present embodiment will be shown below.
[0044]
Magnification of zoom lens of this embodiment 9.50 times
Focal length f of the zoom lens according to the present embodiment f = 5.65 to 53.68
F number = 2.851〜 (3.225〜) 2.931
Incident half angle of view = 32 °
f1 = 35.7500
f2 = -7.0574
f3 = 31.9109
f4 = 17.1900
fw = 5.6483
ν1 = 58.0
[0045]
r₁= 55.2593
  d₁= 1.2 n_d1= 1.85505 ν_d1= 23.78
r₂= 28.1227
  d₂= 5.4 n_d2= 1.59142 ν_d2= 61.25
r_Three= -240.2896
  d_Three= 0.2
r_Four= 24.8402
  d_Four= 3.25 n_d3= 1.73234 ν_d3= 54.67
r_Five= 72.0613
  d_Five= 0.9789 (wide angle), 13.1220 (middle), 21.2174 (telephoto)
r₆= 36.9978
  d₆= 0.6 n_d4= 1.88815 ν_d4= 40.80
r₇= 7.9946
  d₇= 2.84
r₈= -15.6357
  d₈= 0.6 n_d5= 1.88815 ν_d5= 40.80
r₉= 10.4132
  d₉= 0.33
r_Ten= 13.4065
  d_Ten= 1.2 n_d6= 1.48914 ν_d6= 70.44
r₁₁= 9.6737
  d₁₁= 2.55 n_d7= 1.85505 ν_d7= 23.78
r₁₂= -95.2948
  d₁₂= 21.7093 (wide angle), 9.5662 (middle), 1.4708 (telephoto)
r₁₃= ∞ (aperture)
  d₁₃= 1.2
r₁₄= 8.846 (Aspherical surface)
  d₁₄= 1.9 n_d8= 1.58547 ν_d8= 59.46
r₁₅= 100.9727 (aspherical surface)
  d₁₅= 0.5
r₁₆= 13.6187
  d₁₆= 1.2 n_d9= 1.85505 ν_d9= 23.78
r₁₇= 8.1571
  d₁₇= 8.3916 (wide angle), 4.4650 (middle), 6.5332 (telephoto)
r₁₈= 21.1821 (aspherical surface)
  d₁₈= 1.7 n_d10= 1.58547 ν_d10= 59.46
r₁₉= -34.0403
  d₁₉= 4.8
r₂₀= 35.1128
  d₂₀= 0.6 n_d11= 1.85505 ν_d11= 23.78
r_{twenty one}= 13.2363
  d_{twenty one}= 2.3 n_d12= 1.51872 ν_d12= 64.20
r_{twenty two}= -24.6176
[0046]
Cone coefficient (K) and aspheric coefficient (A_Four, A₆, A₈, A_Ten)
14th page
K = 0
A_Four= -8.67112 × 10^-Five, A₆= -1.00797 × 10^-Five,
A₈= 7.74938 × 10^-7, A_Ten= -2.38207 × 10^-8
15th page
K = 0
A_Four= 3.36611 × 10^-Five, A₆= -9.18955 × 10^-6,
A₈= 8.23113 × 10^-7, A_Ten= -2.58259 × 10^-8
18th page
K = 0
A_Four= -7.96380 × 10^-Five, A₆= 8.75294 × 10^-7,
A₈= -4.69443 × 10^-8, A_Ten= 9.9761 × 10^-Ten
[0047]
  Next, aberration diagrams of the zoom lens of the present embodiment are shown. FIG. 2 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the wide-angle end (infinity). FIG. 3 is a diagram showing coma aberration at the wide-angle end (infinity). FIG. 4 is a diagram showing spherical aberration, field curvature, distortion, and lateral chromatic aberration at an intermediate magnification (infinity). FIG. 5 is a diagram showing coma aberration at an intermediate magnification (infinity). FIG. 6 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (infinity). FIG. 7 is a diagram showing coma aberration at the telephoto end (infinity). FIG. 8 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (object distance 90 cm). FIG. 9 is a diagram showing coma aberration at the telephoto end (object distance 90 cm).
[0048]
(Embodiment 2)
  FIG. 10 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the present embodiment. FIG. 10A shows the state at the wide-angle end, FIG. 10B shows the intermediate magnification, and FIG. 10C shows the state at the telephoto end. Similarly to the zoom lens described in the first embodiment, the zoom lens according to the present embodiment also includes a first lens group 21 having a positive refractive power and a second lens having a negative refractive power in order from an object side (not shown). A lens group 22, a third lens group 23 having a positive refractive power, and a fourth lens group 24 having a positive refractive power are arranged. The first lens group 21 includes two convex lenses. The second lens group 22 includes a first lens 221 that is a concave lens, a second lens 222 that is a concave lens, a third lens 223 that is a concave lens, and a fourth lens 224 that is a convex lens. The lens 224 is cemented. The third lens group 23 includes one convex lens and one concave lens. A diaphragm 25 is disposed between the second lens group 22 and the third lens group 23.
[0049]
  Various numerical data related to the zoom lens according to the present embodiment will be shown below.
[0050]
Magnification of the zoom lens of this embodiment: 9.48 times
Focal length f = 5.66 to 53.67 of the zoom lens of the present embodiment
F number = 2.857 to 3.227
Incident half angle of view = 32 °
f1 = 37.2261
f2 = -7.5288
f3 = 38.4603
f4 = 15.66483
fw = 5.6570
ν1 = 58.0
[0051]
r₁= 61.1146
  d₁= 1.2 n_d1= 1.85505 ν_d1= 23.78
r₂= 30.0245
  d₂= 5.5 n_d2= 1.59142 ν_d2= 61.25
r_Three= -196.9376
  d_Three= 0.2
r_Four= 25.2601
  d_Four= 3.3 n_d3= 1.73234 ν_d3= 54.67
r_Five= 69.5156
  d_Five= 1.0167 (wide angle), 13.0955 (middle), 22.2022 (telephoto)
r₆= 37.7751
  d₆= 0.6 n_d4= 1.88815 ν_d4= 40.80
r₇= 8.8107
  d₇= 2.55
r₈= -20.0947
  d₈= 0.6 n_d5= 1.88815 ν_d5= 40.80
r₉= 11.2114
  d₉= 0.9
r_Ten= 18.1618
  d_Ten= 1.1 n_d6= 1.49845 ν_d6= 81.61
r₁₁= 10.5726
  d₁₁= 2.2 n_d7= 1.85505 ν_d7= 23.78
r₁₂= -1147.4489
  d₁₂= 22.3782 (wide angle), 10.3005 (middle), 1.1939 (telephoto)
r₁₃= ∞ (aperture)
  d₁₃= 1.2
r₁₄= 8.9975 (aspherical surface)
  d₁₄= 2.6 n_d8= 1.59142 ν_d8= 61.25
r₁₅= 32.2314 (Aspherical surface)
  d₁₅= 0.5
r₁₆= 16.3624
  d₁₆= 1.8 n_d9= 1.85505 ν_d9= 23.78
r₁₇= 9.6576
  d₁₇= 6.4063 (wide angle), 2.7663 (middle), 4.9965 (telephoto)
r₁₈= 17.5381 (aspherical surface)
  d₁₈= 4.0 n_d10= 1.59142 ν_d10= 61.25
r₁₉= -24.6165
  d₁₉= 3.0
r₂₀= 32.4766
  d₂₀= 3.0 n_d11= 1.85505 ν_d11= 23.78
r_{twenty one}= 10.8426
  d_{twenty one}= 2.8 n_d12= 1.48914 ν_d12= 70.44
r_{twenty two}= -26.6251
[0052]
Cone coefficient (K) and aspheric coefficient (A_Four, A₆, A₈, A_Ten)
14th page
K = 0
A_Four= 6.95003 × 10^-6, A₆= -3.59029 × 10^-7,
A₈= 3.27528 × 10^-7, A_Ten= -6.29916 × 10^-9
15th page
K = 0
A_Four= 1.65458 × 10^-Four, A₆= 1.49779 × 10^-6,
A₈= 4.30574 × 10^-7, A_Ten= -7.15332 × 10^-9
18th page
K = 0
A_Four= -1.00469 × 10^-Four, A₆= 1.09743 × 10^-7,
A₈= 1.04995 × 10^-8, A_Ten= -3.22932 × 10^-Ten
[0053]
  Next, aberration diagrams of the zoom lens of the present embodiment are shown. FIG. 11 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the wide-angle end (infinity). FIG. 12 is a diagram showing coma aberration at the wide-angle end (infinity). FIG. 13 is a diagram showing spherical aberration, field curvature, distortion, and lateral chromatic aberration at an intermediate magnification (infinity). FIG. 14 is a diagram showing coma aberration at an intermediate magnification (infinity). FIG. 15 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (infinity). FIG. 16 is a diagram showing coma aberration at the telephoto end (infinity). FIG. 17 is a diagram showing spherical aberration, curvature of field, distortion, and chromatic aberration of magnification at the telephoto end (object distance 90 cm). FIG. 18 is a diagram showing coma aberration at the telephoto end (object distance 90 cm).
[0054]
(Embodiment 3)
  FIG. 19 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the present embodiment. FIG. 19A shows the state at the wide angle end, FIG. 19B shows the intermediate magnification, and FIG. 19C shows the state at the telephoto end. The zoom lens according to the present embodiment includes, in order from an object side (not shown), a first lens group 31 having a positive refractive power, a second lens group 32 having a negative refractive power, and a first lens group having a positive refractive power. A three lens group 33 and a fourth lens group 34 having a positive refractive power are arranged. The first lens group 31 includes three convex lenses. The second lens group 32 includes a first lens 321 that is a concave lens, a second lens 322 that is a concave lens, a third lens 323 that is a concave lens, and a fourth lens 324 that is a convex lens. The lens 324 is cemented. The third lens group 33 includes one convex lens and one concave lens. A diaphragm 35 is disposed between the second lens group 32 and the third lens group 33.
[0055]
  Various numerical data related to the zoom lens according to the present embodiment will be shown below.
[0056]
Magnification of the zoom lens of this embodiment: 9.48 times
Focal length f = 5.66 to 53.67 of the zoom lens of the present embodiment
F number = 2.849-3.247
Incident half angle of view = 32 °
f1 = 33.9268
f2 = -6.9947
f3 = 34.3661
f4 = 15.3822
fw = 5.6702
ν1 = 62.9
[0057]
r₁= 132.8947
  d₁= 1.2 n_d1= 1.85505 ν_d1= 23.78
r₂= 38.4369
  d₂= 5.0 n_d2= 1.48914 ν_d2= 70.44
r_Three= 2843.4109
  d_Three= 0.15
r_Four= 45.8027
  d_Four= 4.1 n_d3= 1.64129 ν_d3= 55.45
r_Five= -744.8634
  d_Five= 0.15
r₆= 25.1072
  d₆= 3.6 n_d4= 1.73234 ν_d4= 54.67
r₇= 60.8619
  d₇= 0.9897 (wide angle), 11.8700 (middle), 20.2683 (telephoto)
r₈= 32.2421
  d₈= 0.6 n_d5= 1.88815 ν_d5= 40.80
r₉= 7.8214
  d₉= 2.5
r_Ten= -15.073
  d_Ten= 0.6 n_d6= 1.88815 ν_d6= 40.80
r₁₁= 11.0702
  d₁₁= 0.7
r₁₂= 16.6021
  d₁₂= 0.6 n_d7= 1.49845 ν_d7= 81.61
r₁₃= 10.2014
  d₁₃= 2.2 n_d8= 1.85505 ν_d8= 23.78
r₁₄= -83.7874
  d₁₄= 21.3653 (wide angle), 10.4854 (middle), 2.0863 (telephoto)
r₁₅= ∞ (aperture)
  d₁₅= 1.2
r₁₆= 9.2069 (Aspherical surface)
  d₁₆= 3.5 n_d9= 1.59142 ν_d9= 61.25
r₁₇= 26.9421
  d₁₇= 0.5
r₁₈= 10.5555
  d₁₈= 1.4 n_d10= 1.85505 ν_d10= 23.78
r₁₉= 7.6401
  d₁₉= 5.2415 (wide angle), 1.7498 (middle), 5.1298 (telephoto)
r₂₀= 12.6455 (aspherical surface)
  d₂₀= 0.2 n_d11= 1.53920 ν_d11= 41.20
r_{twenty one}= 16.5803
  d_{twenty one}= 4.2 n_d12= 1.51872 ν_d12= 64.20
r_{twenty two}= -26.1174
  d_{twenty two}= 0.5
r_{twenty three}= 30.8552
  d_{twenty three}= 0.8 n_d13= 1.85505 ν_d13= 23.78
r_{twenty four}= 10.6135
  d_{twenty four}= 2.2 n_d14= 1.48914 ν_d14= 70.44
r_{twenty five}= -33.7425
  d_{twenty five}= 1.5691 (wide angle), 5.0620 (middle), 1.6724 (telephoto)
[0058]
Cone coefficient (K) and aspheric coefficient (A_Four, A₆, A₈, A_Ten)
16th page
K = 0
A_Four= -8.29618 × 10^-Five, A₆= -3.92604 × 10^-6,
A₈= 2.89772 × 10^-7, A_Ten= -1.00233 × 10^-8
20th page
K = 0
A_Four= -1.51158 × 10^-Four, A₆= 7.04117 × 10^-7,
A₈= -5.67365 × 10^-9, A_Ten= -2.05944 × 10^-Ten
[0059]
  Next, aberration diagrams of the zoom lens of the present embodiment are shown. FIG. 20 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the wide-angle end (infinity). FIG. 21 is a diagram showing coma aberration at the wide-angle end (infinity). FIG. 22 is a diagram showing spherical aberration, field curvature, distortion, and lateral chromatic aberration at an intermediate magnification (infinity). FIG. 23 is a diagram showing coma aberration at an intermediate magnification (infinity). FIG. 24 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (infinity). FIG. 25 is a diagram showing coma aberration at the telephoto end (infinity). FIG. 26 is a diagram showing spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (object distance: 80 cm). FIG. 27 is a diagram showing coma aberration at the telephoto end (object distance of 80 cm).
[0060]
  In the above numerical data, r₁, R₂,... Are the radii of curvature of each lens or diaphragm surface, d₁, D₂,... Are the thicknesses of the respective lenses or diaphragms or their surface spacing, n_d1, N_d2,... Are the refractive indices of the d-line of each lens, ν_d1, Ν_d2,... Indicate the Abbe number of each lens.
[0061]
  Each of the aspherical shapes is expressed by the following equation when the X axis is taken in the optical axis direction, the Y axis is taken in the direction perpendicular to the optical axis, and the light traveling direction is positive.
[0062]
[Expression 1]

[0063]
  Where r is the paraxial radius of curvature, K is the cone coefficient, A_Four, A₆, A₈, A_TenAre the 4th, 6th, 8th and 10th order aspherical coefficients, respectively.
[0064]
  As described above, according to the present invention, it is possible to provide a zoom lens having a wide angle of view with a short overall length and a small front lens diameter while having a high zoom ratio of about 10. In addition, this zoom lens has stable imaging performance in the entire zoom range. In particular, fluctuations in field curvature and chromatic aberration are reduced when focusing at a short distance of about 1 m at the telephoto end. Therefore, the zoom lens of the present invention can sufficiently cope with a small-sized image sensor having a large number of pixels, and is particularly suitable for a digital still camera and a video camera that are becoming increasingly compact in recent years.
[0065]
  The embodiment of the present invention has been described with reference to the drawings. However, the present invention is not limited to the matters shown in this embodiment, and can be changed or improved based on the description of the scope of claims.
[0066]
【The invention's effect】
  As described above, according to the present invention, it is possible to provide a zoom lens that is sufficiently compact and has high optical performance with a high zoom ratio. This zoom lens is particularly suitable for a compact digital still camera or video camera equipped with an image sensor having a small size and a large number of pixels.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to a first embodiment;
FIG. 2 is a diagram illustrating spherical aberration, curvature of field, distortion, and chromatic aberration of magnification at the wide angle end (infinity) of the zoom lens according to the first embodiment;
FIG. 3 is a diagram illustrating coma aberration at the wide-angle end (infinity) of the zoom lens according to the first embodiment;
FIG. 4 is a diagram illustrating spherical aberration, field curvature, distortion, and chromatic aberration of magnification at an intermediate magnification (infinity) of the zoom lens according to the first embodiment;
FIG. 5 is a diagram illustrating coma aberration at an intermediate magnification (infinity) of the zoom lens according to the first embodiment;
FIG. 6 is a diagram illustrating spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (infinity) of the zoom lens according to the first embodiment;
FIG. 7 is a diagram illustrating coma aberration at the telephoto end (infinity) of the zoom lens according to the first embodiment;
FIG. 8 is a diagram illustrating spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (object distance of 90 cm) of the zoom lens according to the first embodiment;
FIG. 9 is a diagram illustrating coma aberration at the telephoto end (object distance of 90 cm) of the zoom lens according to the first embodiment;
FIG. 10 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the second embodiment;
FIG. 11 is a diagram illustrating spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the wide-angle end (infinity) of the zoom lens according to the second embodiment;
FIG. 12 is a diagram illustrating coma aberration at the wide-angle end (infinity) of the zoom lens according to the second embodiment;
FIG. 13 is a diagram illustrating spherical aberration, field curvature, distortion, and chromatic aberration of magnification at an intermediate magnification (infinity) of the zoom lens according to the second embodiment;
FIG. 14 is a diagram illustrating coma aberration at an intermediate magnification (infinity) of the zoom lens according to the second embodiment;
FIG. 15 is a diagram illustrating spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (infinity) of a zoom lens according to the second embodiment;
FIG. 16 is a diagram illustrating coma aberration at the telephoto end (infinity) of the zoom lens according to the second embodiment;
FIG. 17 is a diagram illustrating spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (object distance of 90 cm) of the zoom lens according to the second embodiment;
FIG. 18 is a diagram illustrating coma aberration at the telephoto end (object distance of 90 cm) of the zoom lens according to the second embodiment;
FIG. 19 is a cross-sectional view along the optical axis showing the configuration of the zoom lens according to the third embodiment;
FIG. 20 is a diagram illustrating spherical aberration, curvature of field, distortion, and chromatic aberration of magnification at the wide-angle end (infinity) of the zoom lens according to the third embodiment.
FIG. 21 is a diagram illustrating coma aberration at the wide-angle end (infinity) of the zoom lens according to the third embodiment;
FIG. 22 is a diagram illustrating spherical aberration, field curvature, distortion, and chromatic aberration of magnification at an intermediate magnification (infinity) of the zoom lens according to the third embodiment;
FIG. 23 is a diagram illustrating coma aberration at an intermediate magnification (infinity) of the zoom lens according to the third embodiment;
FIG. 24 is a diagram illustrating spherical aberration, curvature of field, distortion, and lateral chromatic aberration at the telephoto end (infinity) of a zoom lens according to the third embodiment.
FIG. 25 is a diagram illustrating coma aberration at the telephoto end (infinity) of the zoom lens according to the third embodiment;
FIG. 26 is a diagram illustrating spherical aberration, curvature of field, distortion, and chromatic aberration of magnification at the telephoto end (object distance of 80 cm) of the zoom lens according to the third embodiment.
FIG. 27 is a diagram illustrating coma aberration at the telephoto end (object distance of 80 cm) of the zoom lens according to the third embodiment;
[Explanation of symbols]
11, 21, 31 First lens group
12, 22, 32 Second lens group
13, 23, 33 Third lens group
14, 24, 34 Fourth lens group
15, 25, 35 aperture
121, 221 and 321 first lens
122, 222, 322 second lens
123, 223, 323 Third lens
124,224,324 Fourth lens
e line
d d line
g g line
S Sagittal image plane
T Meridional image

Claims (6)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens groups are arranged,
A zoom lens, wherein zooming is performed by moving the second lens and the fourth lens group in a direction along an optical axis, and satisfies the following conditional expression:
1.2 <| f2 / fw | <1.4
6.2 <f1 / fw <7.2
5.5 <f3 / fw <7.2
2.6 <f4 / fw <3.1
Where f2 is the focal length of the second lens group, f1 is the focal length of the first lens group, f3 is the focal length of the third lens group, f4 is the focal length of the fourth lens group, fw represents the focal length at the short focal end of the zoom lens. The first lens group includes at least two or more convex lenses, and satisfies the following conditional expression when an average value of Abbe numbers of convex lenses included in the first lens group is ν1. The zoom lens according to claim 1 .
58 ≦ ν1 <65 The third lens group includes at least one convex lens and at least one concave lens, and at least one of the lenses included in the third lens group has an aspheric surface. The zoom lens according to claim 1 or 2 . The zoom lens according to claim 1, wherein an aspherical surface is formed on at least one of the lenses included in the fourth lens group . The second lens group includes, in order from the object side, a first lens that is a concave lens, a second lens that is a concave lens, a third lens that is a concave lens, and a fourth lens that is a convex lens. The zoom lens according to claim 1, wherein four lenses are joined . The first lens group includes at least two convex lenses;
In the second lens group, a concave lens first lens, a concave lens second lens, a concave lens third lens, and a convex lens fourth lens are arranged in this order from the object side, and the third lens and the fourth lens are cemented together. Has been formed,
The third lens group includes at least one convex lens and at least one concave lens, and at least one of the lenses included in the third lens group has an aspheric surface. ,
In the fourth lens group, at least one of the lenses included in the fourth lens group has an aspheric surface,
When zooming from the short focus end to the long focus end by moving the second lens group and the fourth lens group in the direction along the optical axis, the fourth lens group is moved to the object side. The zoom lens according to claim 1, wherein the fourth lens group is moved in a direction along the optical axis when moving to the image side and performing focusing .

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