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CN-121995610-A - Variable magnification imaging optical system

CN121995610ACN 121995610 ACN121995610 ACN 121995610ACN-121995610-A

Abstract

The invention provides a zoom imaging optical system which can realize miniaturization and light weight, inhibit chromatic aberration of magnification and chromatic aberration on an axis during zooming, realize high speed during focusing and have good optical performance from infinity to very close position in the whole zooming area. A magnification-varying imaging optical system is composed of a1 st lens group (G1) having positive refractive power, a2 nd lens group (G2) having positive refractive power, a 3 rd lens group (G3) having negative refractive power, an intermediate Group (GM) including one or more lens groups and an aperture stop (S), a focusing Group (GF), and a subsequent Group (GR) composed of one lens group, which are arranged in this order from the object side, the interval between adjacent lens groups being varied at the time of magnification variation, and the focusing Group (GF) being moved along the optical axis when focusing from an infinitely distant object to a close object.

Inventors

  • Ogino Motegi

Assignees

  • 株式会社适马

Dates

Publication Date
20260508
Application Date
20250225
Priority Date
20241107

Claims (20)

  1. 1. A variable magnification imaging optical system is characterized in that, The lens system is composed of a1 st lens group (G1) having positive refractive power, a 2 nd lens group (G2) having positive refractive power, a 3 rd lens group (G3) having negative refractive power, an intermediate Group (GM) including one or more lens groups and an aperture stop (S), a focusing Group (GF), and a subsequent Group (GR) composed of one lens group, which are sequentially arranged from an object side, the interval between adjacent lens groups is changed at the time of zooming, and the focusing Group (GF) moves along an optical axis when focusing from an infinity object to a close object.
  2. 2. The variable magnification imaging optical system according to claim 1, wherein, More than one concave lens satisfying the following condition (1) is arranged between the aperture diaphragm (S) and the subsequent Group (GR), (1) ΔPgFLnSr>0.013 Δ PgFLnSr is the anomalous dispersion of the concave lens arranged between the aperture stop (S) and the subsequent Group (GR).
  3. 3. The variable magnification imaging optical system according to claim 1, wherein, When the magnification is changed from the wide-angle end to the telephoto end, the 1 st lens group (G1) moves to the object side, the interval between the 1 st lens group (G1) and the 2 nd lens group (G2) increases, and the interval between the 2 nd lens group (G2) and the 3 rd lens group (G3) decreases.
  4. 4. The variable magnification imaging optical system according to claim 1, wherein, When the magnification is changed from the wide-angle end to the telephoto end, the 2 nd lens group (G2) moves to the image side, the interval between the 1 st lens group (G1) and the 2 nd lens group (G2) increases, and the interval between the 2 nd lens group (G2) and the 3 rd lens group (G3) decreases.
  5. 5. The variable magnification imaging optical system according to claim 1, wherein, The 1 st lens group (G1) includes a concave lens satisfying the following conditional expression (2), (2)ndLN1<1.80 NdLN1 is the refractive index of the concave lens having the highest refractive index included in the 1 st lens group (G1).
  6. 6. The variable magnification imaging optical system according to claim 1, wherein, The following conditional expression (3) is satisfied, (3)0.005<DG1G2W/DG1G2T<0.400 DG1G2W is an interval on the optical axis between the 1 st lens group (G1) and the 2 nd lens group (G2) at the infinity wide-angle end, DG1G2T is an interval on the optical axis between the 1 st lens group (G1) and the 2 nd lens group (G2) at the infinity side.
  7. 7. The variable magnification imaging optical system according to claim 1, wherein, The following conditional expression (4) is satisfied, (4)1.00<DG2G3W/DG2G3T<80.00 DG2G3W is an interval on the optical axis between the 2 nd lens group (G2) and the 3 rd lens group (G3) at the infinity wide-angle end, DG2G3T is an interval on the optical axis between the 2 nd lens group (G2) and the 3 rd lens group (G3) at the infinity end.
  8. 8. The variable magnification imaging optical system according to claim 1, wherein, The following conditional expression (5) is satisfied, (5)0.01<DG1G2W/DG2G3W<2.00 DG1G2W is an interval on the optical axis between the 1 st lens group (G1) and the 2 nd lens group (G2) at the infinity wide-angle end, DG2G3W is an interval on the optical axis between the 2 nd lens group (G2) and the 3 rd lens group (G3) at the infinity wide-angle end.
  9. 9. The variable magnification imaging optical system according to claim 1, wherein, The following conditional expression (6) is satisfied, (6)2.0<DG1G2T/DG2G3T<200.0 DG1G2T is an interval on the optical axis between the 1 st lens group (G1) and the 2 nd lens group (G2) at the infinity side, DG2G3T is an interval on the optical axis between the 2 nd lens group (G2) and the 3 rd lens group (G3) at the infinity end.
  10. 10. The variable magnification imaging optical system according to claim 1, wherein, The following conditional expression (7) is satisfied, (7)1.2<DG2Sw/DG2St<5.0 DG2Sw is a distance from the surface of the lens closest to the object side of the 2 nd lens group (G2) to the aperture stop (S) at the wide angle end, DG2St is a distance from the surface of the lens closest to the object side of the 2 nd lens group (G2) to the aperture stop (S) at the telephoto end.
  11. 11. The variable magnification imaging optical system according to claim 1, wherein, The 2 nd lens group (G2) satisfies the following conditional expression (8), (8)0.2<g2AXhW/g2AXhT<1.5 G2AXhW is the height of the on-axis marginal ray at the infinity wide-angle end with the aperture stop open on the face of the front of the 2 nd lens group (G2), G2AXhT is the height of the on-axis marginal ray at the infinite telephoto end, where the stop is open, on the face of the front of the 2 nd lens group (G2).
  12. 12. The variable magnification imaging optical system according to claim 1, wherein, The 2 nd lens group (G2) satisfies the following conditional expression (9) and (10), (9)-1.8<(g2OAhW/Wih)-(g2OAhT/Tih)<-0.3 (10)0.6<|g2OAhW/g2AXhT|<2.5 Wih is the imaging height of the off-axis chief ray at the maximum field angle at the wide-angle end of infinity, Tih is the imaging image height of the off-axis chief ray at the maximum field angle at the far-end of infinity, G2OAhW is the height of the off-axis chief ray of the maximum field angle at the wide-angle end of infinity on the face of the front head of the 2 nd lens group (G2), G2OAhT is the height of the off-axis chief ray at the maximum field angle at the infinity end on the face of the front head of the 2 nd lens group (G2), G2AXhT is the height of the on-axis marginal ray at the infinite telephoto end, where the stop is open, on the face of the front of the 2 nd lens group (G2).
  13. 13. The variable magnification imaging optical system according to claim 1, wherein, The 2 nd lens group (G2) includes more than one concave lens.
  14. 14. The variable magnification imaging optical system according to claim 1, wherein, The 2 nd lens group (G2) comprises at least one concave lens satisfying the following conditional expression (11), (11)ΔPgFLg2>0.0090 Δ PgFLg2 is the anomalous dispersion of the concave lens having the largest anomalous dispersion among the concave lenses included in the 2 nd lens group (G2).
  15. 15. The variable magnification imaging optical system according to claim 1, wherein, The subsequent Group (GR) comprises at least one concave lens satisfying the following conditional expression (12), (12) delta PgFnLr >0.009 Δ PgFnLr is the anomalous dispersion of the concave lens of the subsequent Group (GR).
  16. 16. The variable magnification imaging optical system according to claim 1, wherein, The subsequent Group (GR) comprises at least one concave lens (13) vdnLr XΔ PgFnLr >0.80 which satisfies the following conditional expression (13) VdnLr is the Abbe number of the concave lens included in the subsequent Group (GR), Δ PgFnLr is the anomalous dispersion of the concave lenses included in the subsequent Group (GR).
  17. 17. The variable magnification imaging optical system according to claim 1, wherein, The subsequent Group (GR) comprises at least one or more convex lenses (14) satisfying the following conditional expression (14) [ delta ] PgFpLr < -0.0010 Δ PgFpLr is the anomalous dispersion of the convex lenses included in the subsequent Group (GR).
  18. 18. The variable magnification imaging optical system according to claim 1, wherein, The two convex lenses counted from the most image side satisfy the following conditional expression (15), (15) ΔPgFprAVE<-0.0010 Δ PgFprAVE is an average value of anomalous dispersion of two convex lenses from the most image side.
  19. 19. The variable magnification imaging optical system according to claim 1, wherein, The 1 st lens group (G1) satisfies the following conditional expression (16), (16)0.18<f1/fT<1.00 F1 is the focal length of the 1 st lens group (G1), FT is the focal length of the variable magnification imaging optical system at the infinity-side.
  20. 20. The variable magnification imaging optical system according to claim 1, wherein, The 2 nd lens group (G2) satisfies the following conditional expression (17), (17)0.1<f2/fT<1.4 F2 is the focal length of the 2 nd lens group (G2), FT is the focal length of the variable magnification imaging optical system at the infinity-side.

Description

Variable magnification imaging optical system Technical Field The present invention relates to a magnification-varying imaging optical system suitable for an imaging optical system used in an imaging apparatus such as a digital camera or a video camera. Background In recent years, there has been a development of a digital camera or video camera without a mirror, and a smart phone or a mobile data terminal is equipped with a high-performance camera. In recent years, the imaging device of a digital still camera or video camera has been further increased in pixel size, and the demand for higher performance of an imaging optical system has been further increased. Patent documents 1 to 3 describe examples of variable magnification imaging optical systems in which the half field angle at the telephoto end is substantially 3 degrees or less. Patent document 1 Japanese patent application laid-open No. 2013-167749 Patent document 2 Japanese patent laid-open publication 2016-080825 Patent document 3 Japanese patent application laid-open No. 2019-020450 In a super-telephoto zoom lens having a narrow angle of view at the telephoto end, in order to improve the usability as a zoom lens, it is necessary to achieve both miniaturization and imaging performance for improving portability, with a large zoom ratio as much as possible. In order to obtain a large zoom ratio, a lens group having positive refractive power is generally disposed on the most object side, and is pushed out to the object side by zooming, whereby the telephoto ratio (the value of the total optical length divided by the focal length) at the telephoto end is increased as much as possible, and the imaging performance at the telephoto end is improved. In the telescopic lens, aberration generated in the lens group of the converging system disposed on the object side is amplified in the lens group at the rear. In the case of a single focus lens, although the imaging performance can be improved by simply suppressing the aberration generated in the converging system on the object side according to the relationship, the aberration varies due to the change in the power arrangement caused by the magnification change in the zoom lens, and therefore, the simplification as in the case of a single focus lens is not possible. In particular, since chromatic aberration of magnification, which is a problem in a lens in a super telescopic region having a narrow angle of view, changes in direction due to magnification, it is important to select an optical material according to a change in power arrangement caused by magnification in order to achieve miniaturization of an optical system while suppressing generation of chromatic aberration of magnification in the entire region of zooming. The optical system described in patent document 1 is an example of a telescopic zoom lens having a fixed total length. Each aberration is suppressed and imaging performance is high in the entire area of zooming, but if the magnification ratio is increased while maintaining imaging performance in a type where the total length is fixed in this way, it results in a significant increase in the optical system, so that it is not preferable. The optical system described in patent document 2 is an example of a variable total length type super-telephoto zoom lens proposed in group 1, but is insufficient in terms of downsizing of the optical system in view of the reduction in flange distance due to the lack of a mirror in recent years because the back focal length (distance from the final lens to the image plane) is large with respect to the total optical length. Further, the variation of chromatic aberration of magnification from the wide-angle end to the telephoto end is large, and correction is insufficient. The optical system described in patent document 3 is an example of a super-telephoto zoom lens corresponding to a short flange distance, but the chromatic aberration of magnification varies greatly from the wide-angle end to the telephoto end, the correction is insufficient, and the suppression of the total optical length at the wide-angle end is also insufficient. Disclosure of Invention The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnification-varying imaging optical system which is reduced in size and weight, suppresses chromatic aberration of magnification and chromatic aberration on the axis at the time of magnification variation, and is capable of achieving high speed at the time of focusing, and has excellent optical performance from infinity to very close to the whole zoom region. In order to solve the above-described problems, in one embodiment of the variable magnification imaging optical system according to the present invention, the lens group G1 having positive refractive power, the lens group G2 having positive refractive power, the lens group G3 having negative refractive power, the intermediate group GM