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JP-7855759-B2 - Optical system and imaging device having the same

JP7855759B2JP 7855759 B2JP7855759 B2JP 7855759B2JP-7855759-B2

Inventors

  • 鈴木 匠

Assignees

  • キヤノン株式会社

Dates

Publication Date
20260508
Application Date
20250404

Claims (14)

  1. It consists of a front group and a back group of positive refractive powers, arranged sequentially from the object side to the image side. In the aforementioned front group, the lens positioned closest to the object has a negative refractive power. For focusing, the front group moves in the optical axis direction, while the rear group remains stationary. In the aforementioned rear group, the final lens positioned closest to the image has a positive refractive power. The front group has an aperture, When the radius of curvature of the object side of the final lens is GLR1, the radius of curvature of the image side is GLR2, the distance between the lens closest to the object and the second lens from the object side in the front group is L12, the distance between the second lens from the object side and the third lens from the object side in the front group is L23 , when the lens is in focus at infinity, the distance along the optical axis from the object-side surface of the lens closest to the object to the aperture is PD, and when the lens is in focus at infinity, the distance along the optical axis from the object-side surface of the lens closest to the object to the image-side surface of the final lens is LD , 0.1<(GLR1+GLR2)/(GLR1-GLR2)<10.0 0.1<L12/L23<5.0 PD/LD<0.45 An optical system characterized by satisfying the following conditional equation.
  2. When the distance from the image-side lens surface to the image plane of the final lens (back focus in air equivalent) is denoted as sk, 0.1<sk/LD<0.5 The optical system according to claim 1, characterized in that it satisfies the following condition.
  3. When the focal length of the first sub-lens group located on the object side of the aperture within the front group is f11, and the focal length of the second sub-lens group located on the image side of the aperture within the front group is f12, -5.0<f11/f12<5.0 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.
  4. When the distance between the front group and the rear group on the optical axis at infinity focus is denoted as LB, 0.05<LB/LD<0.60 The optical system according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.
  5. When the focus sensitivity of the front group at infinity is denoted as ESinf, 0.2<ESinf<2.0 The optical system according to any one of claims 1 to 4, characterized in that it satisfies the following conditional expression.
  6. When the focal length of the first sub-lens group located on the object side of the aperture within the front group is f11, and the focal length of the entire system is f, -3.0<f11/f<12.0 The optical system according to any one of claims 1 to 5 , characterized in that it satisfies the following conditional expression.
  7. The optical system according to any one of claims 1 to 6 , characterized in that the first sub-lens group located on the object side of the aperture within the front group includes three lenses.
  8. The optical system according to claim 7 , characterized in that the first sub-lens group includes a lens having positive refractive power.
  9. When the radius of curvature of the image-side surface of the second lens from the object side is G2R2, and the radius of curvature of the object-side surface of the third lens from the object side is G3R1, -8.0<(G2R2+G3R1)/(G2R2-G3R1)<-0.1 The optical system according to any one of claims 1 to 8 , characterized in that it satisfies the following conditional expression.
  10. When the focal length of the lens closest to the object and having negative refractive power within the front group is fGn1, and the focal length of the first sub-lens group located closer to the object than the aperture within the front group is f11, 0.1<fGn1/f11<7.0 The optical system according to any one of claims 1 to 9, characterized in that it satisfies the following conditional expression.
  11. When νdn is the average Abbe number of the materials of the negative refractive power lenses located on the object side of the aperture within the front group, and νdp is the average Abbe number of the materials of the positive refractive power lenses located on the object side of the aperture within the front group, 0.3<νdn/νdp<4.5 The optical system according to any one of claims 1 to 10 , characterized in that it satisfies the following conditional expression.
  12. The optical system according to any one of claims 1 to 11 , characterized in that the lens positioned closest to the object in the front group is a negative meniscus lens with its convex surface facing the object.
  13. It consists of a front group and a back group of positive refractive powers, arranged sequentially from the object side to the image side. In the aforementioned front group, the lens positioned closest to the object has a negative refractive power. For focusing, the front group moves in the optical axis direction, while the rear group remains stationary. In the aforementioned rear group, the final lens positioned closest to the image has a positive refractive power. The front group has an aperture, When the radius of curvature of the final lens on the object side is GLR1, the radius of curvature of the image side is GLR2, the distance between the lens closest to the object and the second lens from the object side in the front group is L12, the distance between the second lens from the object side and the third lens from the object side in the front group is L23, the focal length of the first sub-lens group located on the object side of the aperture in the front group is f11, the focal length of the second sub-lens group located on the image side of the aperture in the front group is f12, the focal length of the lens closest to the object with negative refractive power in the front group is fGn1, and the focal length of the first sub-lens group located on the object side of the aperture in the front group is f11, 0.1<(GLR1+GLR2)/(GLR1-GLR2)<10.0 0.1<L12/L23<5.0 -5.0<f11/f12<5.0 0.1<fGn1/f11<7.0 An optical system characterized by satisfying the following conditional equation.
  14. An imaging device characterized by comprising an optical system according to any one of claims 1 to 13, and an image sensor that receives an image formed by the optical system.

Description

This invention relates to an optical system and an imaging device having the same. As a photographic optical system with a wide field of view, a so-called retrofocus type photographic optical system is known, in which an optical system with negative refractive power is placed on the object side and an optical system with positive refractive power is placed on the image side. This is used, for example, in fixed-focal-length wide-angle lenses. Furthermore, in digital cameras and video cameras, the pixel count of solid-state image sensors such as CCDs and CMOS sensors is increasing, requiring high optical performance, including chromatic aberration, in photographic lenses, while also leading to miniaturization. Japanese Patent Publication No. 2017-009644Japanese Patent Publication No. 2014-055992 This is a cross-sectional view of the lens in Example 1 when the object distance is infinite.This is an aberration diagram for Example 1 when the object distance is infinite.This is a cross-sectional view of the lens in Example 2 when the object distance is infinite.This is an aberration diagram for Example 2 when the object distance is infinite.This is a cross-sectional view of the lens in Example 3 when the object distance is infinite.This is an aberration diagram for Example 3 when the object distance is infinite.This is a cross-sectional view of the lens in Example 4 when the object distance is infinite.This is an aberration diagram for Example 4 when the object distance is infinite.This is a cross-sectional view of the lens in Example 5 when the object distance is infinite.This is an aberration diagram for Example 5 when the object distance is infinite.This is a schematic diagram of the main components of the imaging device of the present invention. Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Figures 1, 3, 5, 7, and 9 are cross-sectional views of the optical systems of Embodiments 1 to 5 of the present invention when the object distance is infinite. Figures 2, 4, 6, 8, and 10 show the aberration diagrams of the optical systems of Embodiments 1 to 5 of the present invention when the object distance is infinite. The optical systems of each embodiment are used in imaging devices such as digital still cameras, video cameras, surveillance cameras, and in-vehicle cameras. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). SP stands for aperture. IP stands for image plane; when used in the optical system of a digital still camera or video camera, it is where the image plane of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed. When used in the optical system of a silver halide film camera, it is where the photosensitive surface of the film is placed. In the aberration diagram, Fno represents the F-number, and ω represents the half-angle of view (degrees). In the spherical aberration diagram, d represents the d-line (wavelength 587.56 nm), and g represents the g-line (wavelength 435.835 nm). In the astigmatism diagram, ΔS is the sagittal image plane at the d line, and ΔM is the meridional image plane at the d line. Distortion is shown for the d line. The chromatic aberration diagram shows lateral chromatic aberration and is shown for the g line. The present invention has a front group of lenses having positive refractive power, arranged sequentially from the object side to the image side, and a rear group having at least one lens with positive refractive power, wherein the distance between the front group and the rear group changes during focusing, and when infinity focus is achieved, the radius of curvature of the object side of the lens with positive refractive power closest to the image is GLR1, and the radius of curvature of the image side is GLR2. 0.1<(GLR1+GLR2)/(GLR1-GLR2)<10.0...(1) It is characterized by satisfying the following conditional expression. In wide-angle lenses, appropriately setting the lens shape closest to the image sensor allows for a longer exit pupil, thus reducing the angle at which off-axis rays enter the image sensor. This reduces the impact of the image sensor's oblique incident light characteristics, enabling a reduction in shading and other distortions. Furthermore, it allows for proper correction of distortion and chromatic aberration, primarily caused by off-axis rays. Additionally, moving the front group along the optical axis during focusing suppresses aberration fluctuations during focusing while simultaneously reducing the weight of the focusing group compared to a single, integrated focusing group. Conditional equation (1) specifies the shape factor of the lens positioned closest to the image. Optimizing the shape allows for both reduction of shading by ensuring sufficient exit pupil length and suppression of various aberration fluctuations during focusing. Exceeding the uppe