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JP-7856565-B2 - Optical systems and optical instruments

JP7856565B2JP 7856565 B2JP7856565 B2JP 7856565B2JP-7856565-B2

Inventors

  • 村谷 真美

Assignees

  • 株式会社ニコン

Dates

Publication Date
20260511
Application Date
20210608
Priority Date
20200709

Claims (16)

  1. It consists of a front group, an aperture, and a rear group, arranged in order from the object side along the optical axis. The aforementioned front group consists of a first lens group having positive refractive power, The aforementioned rear group consists of a second lens group that constitutes a first focusing lens group having negative refractive power, arranged in order from the object side, a third lens group having positive refractive power, a fourth lens group that constitutes a second focusing lens group having negative refractive power, and a fifth lens group having negative refractive power. When focusing occurs, the second lens group and the fourth lens group move along the optical axis, and the spacing between adjacent lens groups changes. An optical system that satisfies the following conditions. 0.63<ST/TL<0.95 0.65<f/(-fF)<1.40 0.05<Bf/TL<0.25 However, ST: distance along the optical axis from the aperture to the image plane TL: total length of the optical system f: focal length of the optical system fF: focal length of the second lens group constituting the first focusing lens group Bf: back focus of the optical system
  2. It consists of a front group, an aperture, and a rear group, arranged in order from the object side along the optical axis. The aforementioned front group consists of a first lens group having positive refractive power, The aforementioned rear group consists of a second lens group that constitutes a first focusing lens group having negative refractive power, arranged in order from the object side, a third lens group having positive refractive power, a fourth lens group that constitutes a second focusing lens group having negative refractive power, and a fifth lens group having negative refractive power. When focusing occurs, the second lens group and the fourth lens group move along the optical axis, and the spacing between adjacent lens groups changes. An optical system that satisfies the following conditions. 0.50<ST/TL<0.95 0.65<(-fF)/fA<1.15 0.65<f/(-fF)<1.40 0.05<Bf/TL<0.25 However, ST: distance along the optical axis from the aperture to the image plane TL: total length of the optical system fF: focal length of the second lens group constituting the first focusing lens group fA: focal length of the front group f: focal length of the optical system Bf: back focus of the optical system
  3. The optical system according to claim 1 or 2, satisfying the following conditional expression. 0.65<f/(-fF)≦1.395
  4. The aforementioned rear group has at least one lens group positioned on the image plane side of the second lens group that constitutes the first focusing lens group , An optical system according to any one of claims 1 to 3 that satisfies the following conditional expression. 0.70<(-fF)/fR<1.80 However, fR: the combined focal length of at least one lens group.
  5. The aforementioned rear group has a subsequent lens group arranged adjacent to the image plane side of the second lens group that constitutes the first focusing lens group , An optical system according to any one of claims 1 to 4 that satisfies the following conditional expression. 0.00<βR1/βF<0.25 However, βR1: Lateral magnification of the subsequent lens group when an object at infinity is in focus βF: Lateral magnification of the second lens group constituting the first focusing lens group when an object at infinity is in focus
  6. An optical system according to any one of claims 1 to 5 that satisfies the following conditional expression. 2.00<TL/(FNO×Bf)<10.00 However, FNO: F-number of the optical system Bf: Back focus of the optical system
  7. The optical system according to any one of claims 1 to 6, wherein the focusing lens group is composed of one negative lens component.
  8. An optical system according to any one of claims 1 to 7 that satisfies the following conditional expression. -2.50<(rFR2+rFR1)/(rFR2-rFR1)<-0.25 However, rFR1: radius of curvature of the lens surface closest to the object in the second lens group constituting the first focusing lens group rFR2: radius of curvature of the lens surface closest to the image plane in the second lens group constituting the first focusing lens group
  9. An optical system according to any one of claims 1 to 8 that satisfies the following conditional expression. 0.90<(rNR2+rNR1)/(rNR2-rNR1)<2.65 However, rNR1: radius of curvature of the object-side lens surface of the lens positioned closest to the image plane in the optical system rNR2: radius of curvature of the image-side lens surface of the lens positioned closest to the image plane in the optical system
  10. An optical system according to any one of claims 1 to 9 that satisfies the following conditional expression. 0.08<1/βF<0.55 However, βF: the lateral magnification of the second lens group constituting the first focusing lens group when an object at infinity is in focus.
  11. An optical system according to any one of claims 1 to 10 that satisfies the following conditional expression. {βF+(1/βF)} -2 <0.15 However, βF: the lateral magnification of the second lens group constituting the first focusing lens group when an object at infinity is in focus.
  12. An optical system according to any one of claims 1 to 11 that satisfies the following conditional expression. 0.003<BLDF/TL<0.060 However, BLDF: the length along the optical axis of the second lens group constituting the first focusing lens group.
  13. An optical system according to any one of claims 1 to 12 that satisfies the following conditional expression. 0.05<βB/βF<0.50 However, βB: Lateral magnification of the rear group when an object at infinity is in focus βF: Lateral magnification of the second lens group constituting the first focusing lens group when an object at infinity is in focus
  14. An optical system according to any one of claims 1 to 13 that satisfies the following conditional expression. 1.00<FNO<3.00 However, FNO: F-number of the optical system.
  15. An optical system according to any one of claims 1 to 14 that satisfies the following conditional expression. 12.00°<2ω<40.00° However, 2ω: the entire field of view of the optical system.
  16. An optical instrument comprising the optical system described in any one of claims 1 to 15.

Description

This invention relates to optical systems and optical instruments . Conventionally, optical systems suitable for photographic cameras, electronic still cameras, video cameras, etc., have been proposed (see, for example, Patent Document 1). In such optical systems, it is required to suppress fluctuations in the angle of view during focusing. Japanese Patent Publication No. 2011-197471 The first optical system according to the present invention consists of a front group, an aperture, and a rear group, arranged in order from the object side along the optical axis, the front group consisting of a first lens group having positive refractive power, the rear group consisting of a second lens group having negative refractive power and arranged in order from the object side, a third lens group having positive refractive power, a fourth lens group having negative refractive power and forming a second lens group having negative refractive power, and a fifth lens group having negative refractive power. When focusing occurs, the second lens group and the fourth lens group move along the optical axis, changing the spacing between adjacent lens groups and satisfying the following condition. 0.63<ST/TL<0.95 0.65<f/(-fF)<1.40 0.05<Bf/TL<0.25 However, ST: distance along the optical axis from the aperture to the image plane TL: total length of the optical system f: focal length of the optical system fF: focal length of the second lens group constituting the first focusing lens group Bf: back focus of the optical system The second optical system according to the present invention consists of a front group, an aperture, and a rear group, arranged in order from the object side along the optical axis. The front group consists of a first lens group having positive refractive power. The rear group consists of a second lens group having negative refractive power, which is arranged closest to the object side, forming a first focusing lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having negative refractive power, which is forming a second focusing lens group having negative refractive power; and a fifth lens group having negative refractive power. When focusing, the second and fourth lens groups move along the optical axis, changing the spacing between adjacent lens groups and satisfying the following condition. 0.50<ST/TL<0.95 0.65<(-fF)/fA<1.15 0.65<f/(-fF)<1.40 0.05<Bf/TL<0.25 However, ST: distance along the optical axis from the aperture to the image plane TL: total length of the optical system fF: focal length of the second lens group constituting the first focusing lens group fA: focal length of the front group f: focal length of the optical system Bf: back focus of the optical system The optical instrument according to the present invention is configured to include the optical system described above. This figure shows the lens configuration of the optical system according to the first embodiment.Figures 2(A) and 2(B) show the aberrations of the optical system according to the first embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the second embodiment.Figures 4(A) and 4(B) show the aberrations of the optical system according to the second embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the third embodiment.Figures 6(A) and 6(B) show the aberrations of the optical system according to the third embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the fourth embodiment.Figures 8(A) and 8(B) show the aberrations of the optical system according to the fourth embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the fifth embodiment.Figures 10(A) and 10(B) show the aberrations of the optical system according to the fifth embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the sixth embodiment.Figures 12(A) and 12(B) show the aberrations of the optical system according to the sixth embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the seventh embodiment.Figures 14(A) and 14(B) show the aberrations of the optical system according to the seventh embodiment when it is focused at infinity and when it is focused at close range, respectively.This figure shows the lens configuration of the optical system according to the eighth embodiment.Figures 16(A) and 16(B) show the