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CN-115598811-B - Optical system and image pickup apparatus having the same

CN115598811BCN 115598811 BCN115598811 BCN 115598811BCN-115598811-B

Abstract

The present disclosure relates to an optical system and an image pickup apparatus having the optical system. The optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power. The distance between adjacent lens units changes during focusing. The second lens unit moves toward the image side during focusing from an object at infinity to a short-distance object. The first lens unit includes a positive lens closest to the object and two or more negative lenses. The second lens unit is composed of a single negative lens. The predetermined condition is satisfied.

Inventors

  • Secondary field is zhang fine
  • HATADA TAKAHIRO

Assignees

  • 佳能株式会社

Dates

Publication Date
20260512
Application Date
20220705
Priority Date
20210708

Claims (8)

  1. 1. An optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power, each distance between adjacent lens units being changed during focusing, Characterized in that the second lens unit moves to the image side during focusing from an object at infinity to an object at a short distance, Wherein the first lens unit comprises a positive lens closest to the object and two or more negative lenses, Wherein the third lens unit is composed of a first subunit having a positive refractive power, a second subunit having a negative refractive power, and a third subunit having a positive refractive power in order from the object side to the image side, Wherein during image stabilization, the second subunit moves in a direction comprising a component in a direction orthogonal to the optical axis, Wherein the second lens unit is composed of a single negative lens, and Wherein the following conditional expression is satisfied: 0.2 < LD1/LD < 0.35 BF/f < 0.25 Where LD1 is a distance on the optical axis from the lens surface of the first lens unit closest to the object to the lens surface of the first lens unit closest to the image plane, LD is a distance on the optical axis from the lens surface of the first lens unit closest to the object to the image plane, f is a focal length of the optical system, and BF is a back focal length of the optical system when focusing on an infinitely distant object.
  2. 2. The optical system according to claim 1, wherein the following conditional expression is satisfied: LD/f < 1.5。
  3. 3. the optical system according to claim 1, wherein the following conditional expression is satisfied: 0.50 < f1/f < 0.85 Where f1 is the focal length of the first lens unit.
  4. 4. The optical system according to claim 1, wherein the following conditional expression is satisfied: -0.65 < f2/f < -0.35 where f2 is the focal length of the second lens unit.
  5. 5. The optical system according to claim 1, wherein the following conditional expression is satisfied: 0.65 < f3/f < 0.95 Where f3 is the focal length of the third lens unit.
  6. 6. The optical system according to claim 1, wherein the following conditional expression is satisfied: 15 < νdG1 < 30 Where νdG1 is the Abbe number of the positive lens.
  7. 7. The optical system of claim 1, wherein the first lens unit and the third lens unit are stationary during focusing.
  8. 8. An image pickup apparatus comprising: the optical system according to any one of claims 1 to 7, and An image sensor configured to receive an image formed by the optical system.

Description

Optical system and image pickup apparatus having the same Technical Field The present disclosure relates to an optical system suitable for a digital video camera, a digital still camera, a broadcasting camera, a film-based camera, a monitoring camera, an in-vehicle camera, and the like. Background A telescopic imaging optical system (telescopic lens) having a long focal length is generally known. The long focal length is, for example, a focal length longer than the size of the effective imaging range. In general, a telephoto lens becomes larger and heavier as a focal length becomes longer. Furthermore, especially longitudinal chromatic aberration and lateral chromatic aberration among various aberrations fluctuate during focusing. Japanese patent laid-open No.2016-151664 discloses a telescopic lens including, in order from an object side to an image side, first to third lens units having positive, negative and positive refractive powers, wherein the second lens unit moves toward the image side during focusing from an object at infinity to a short-distance object (closest or closest object). By appropriately setting the refractive powers of the sub-units in the third lens unit, the telescopic lens disclosed in JP 2016-151664 can be made light and various aberrations can be satisfactorily corrected. In the telescopic lens disclosed in JP 2016-151664, the second lens unit as a focusing unit includes a single positive lens and a single negative lens, or a single positive lens and two negative lenses. But the focusing unit has a large number of lenses and becomes heavy. Further, the driving system for the focusing unit requires a heavy load and it is difficult to achieve high-speed focusing. Disclosure of Invention The present disclosure provides an optical system and an image pickup apparatus having the same, each of which is capable of reducing the weight of a focusing unit. An optical system according to one aspect of the present disclosure includes, in order from an object side to an image side, a first lens unit having a positive refractive power, an aperture stop, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power. The distance between adjacent lens units changes during focusing. The second lens unit moves toward the image side during focusing from an object at infinity to a short-distance object. The first lens unit includes a positive lens closest to the object and two or more negative lenses. The second lens unit is composed of a single negative lens. The following conditional expression is satisfied: 0.2<LD1/LD<0.4 BF/f<0.25 Where LD1 is a distance on the optical axis from the lens surface of the first lens unit closest to the object to the lens surface of the first lens unit closest to the image plane, LD is a distance on the optical axis from the lens surface of the first lens unit closest to the object to the image plane, f is a focal length of the optical system, and BF is a back focal length of the optical system upon focusing on an infinitely distant object. An image pickup apparatus according to another aspect of the present disclosure includes the above optical system, and an image sensor configured to receive an image formed by the optical system. Other features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Drawings Fig. 1 is a cross-sectional view of an imaging optical system according to example 1 in an in-focus state on an object at infinity. Fig. 2A and 2B are aberration diagrams when in focus on an object at infinity and a short-distance object according to example 1. Fig. 3 is a cross-sectional view of the imaging optical system according to example 2 in an in-focus state on an object at infinity. Fig. 4A and 4B are aberration diagrams when in focus on an object at infinity and a short-distance object according to example 2. Fig. 5 is a cross-sectional view of the imaging optical system according to example 3 in an in-focus state on an object at infinity. Fig. 6A and 6B are aberration diagrams when in focus on an object at infinity and a short-distance object according to example 3. Fig. 7 is a cross-sectional view of the imaging optical system according to example 4 in an in-focus state on an object at infinity. Fig. 8A and 8B are aberration diagrams when in focus on an object at infinity and a short-distance object according to example 4. Fig. 9 is a schematic diagram of an image pickup apparatus. Detailed Description Referring now to the drawings, a detailed description will be given of embodiments according to the present disclosure. Corresponding elements in the respective drawings will be denoted by the same reference numerals, and repetitive description thereof will be omitted. Fig. 1, 3, 5, and 7 are sectional views of an imaging optical system (optical system) according to examples 1 to 4 in an in-focus state on an inf