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US 2020/0026060 A1Published application
Objective optical system, image pickup apparatus, and endoscope
AssigneeOlympus Corporation
InventorHideyasu Takato
Life of this patent
Estimating the term…
Abstract
An objective optical system consists of, in order from an object side, a first lens group having a negative refractive power, which is stationary all the time, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, which is stationary all the time. At a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side and the third lens group moves toward an image side. The following conditional expressions (1), (5), and (7) are satisfied: 2<fG2/f<8 (1) 0.2<(t34f−t34n)/f<0.5 (5) −8<fG1/f<−2 (7).
Claims19
An objective optical system consisting of, in order from an object side to an image side:
- a first lens group having a negative refractive power, which is stationary all the time;
- a second lens group having a positive refractive power;
- a third lens group having a negative refractive power, and
- a fourth lens group having a positive refractive power, which is stationary all the time, wherein
- at a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side, and the third lens group moves toward the image side, and
- the following conditional expressions (1), (5), and (7) are satisfied:
- 2<fG2/f<8 (1)
- 0.2<(t34f−t34n)/f<0.5 (5)
- −8<fG1/f<−2 (7)
- where,
- fG2 denotes a focal length of the second lens group,
- f denotes a focal length of the overall objective optical system at a time of focusing to an object point at a long distance,
- t34f denotes a distance between the third lens group and the fourth lens group at the time of focusing to an object point at a long distance,
- t34n denotes a distance between the third lens group and the fourth lens group at a time of focusing to an object point at a short distance, and
- fG1 denotes a focal length of the first lens group.
12 more elements
An image pickup apparatus comprising,
- an image sensor, and
- an objective optical system, wherein
- the objective optical system consisting of, in order from an object side to an image side,
- a first lens group having a negative refractive power, which is stationary all the time,
- a second lens group having a positive refractive power,
- a third lens group having a negative refractive power, and
- a fourth lens group having a positive refractive power, which is stationary all the time, wherein
- at a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side, and the third lens group moves toward the image side, and
- the following conditional expressions (1), (5), and (7) are satisfied:
- 2<fG2/f<8 (1)
- 0.2<(t34f−t34n)/f<0.5 (5)
- −8<fG1/f<−2 (7)
- where,
- fG2 denotes a focal length of the second lens group,
- f denotes a focal length of the overall objective optical system at a time of focusing to an object point at a long distance,
- t34f denotes a distance between the third lens group and the fourth lens group at the time of focusing to an object point at a long distance,
- t34n denotes a distance between the third lens group and the fourth lens group at a time of focusing to an object point at a short distance, and
- fG1 denotes a focal length of the first lens group.
15 more elements
An endoscope comprising,
- an image sensor, and
- an objective optical system, wherein
- the objective optical system consisting of, in order from an object side to an image side,
- a first lens group having a negative refractive power, which is stationary all the time,
- a second lens group having a positive refractive power,
- a third lens group having a negative refractive power, and
- a fourth lens group having a positive refractive power, which is stationary all the time, wherein
- at a time of focusing from an object point at a long distance to an object point at a short distance, the second lens group moves toward the object side, and the third lens group moves toward the image side, and
- the following conditional expressions (1), (5), and (7) are satisfied:
- 2<fG2/f<8 (1)
- 0.2<(t34f−t34n)/f<0.5 (5)
- −8<fG1/f<−2 (7)
- where,
- fG2 denotes a focal length of the second lens group,
- f denotes a focal length of the overall objective optical system at a time of focusing to an object point at a long distance,
- t34f denotes a distance between the third lens group and the fourth lens group at the time of focusing to an object point at a long distance,
- t34n denotes a distance between the third lens group and the fourth lens group at a time of focusing to an object point at a short distance, and
- fG1 denotes a focal length of the first lens group.
15 more elements
Dependencies are inferred from the claim text.