Optical system and image pickup apparatus having the same

Patent metadata

Field	Value
Publication number	US-10620401-B2
Application number	US-201715606843-A
Country	US
Kind code	B2
Filing date	May 26, 2017
Priority date	Jun 1, 2016
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

An optical system includes a plurality of lenses. The distance from the object side lens surface of a lens arranged an the most object side to the image plane is longer than the focal length of the entire system. The material of a positive lens G1p arranged on the most object side among positive lenses included in the optical system, and the arrangement and material of a negative lens Gn located on the most object side among negative lenses arranged an the image side of the positive lens G1p are appropriately set.

First claim

What is claimed is:

1. An optical system comprising:
a positive lens G 1 p ; and
a negative lens Gn located on a most object side among negative lenses arranged on an image side of the positive lens G 1 p,
wherein the positive lens G 1 p is a positive lens located on a most object side among positive lenses included in the optical system,
wherein the optical system does not include a diffractive optical element, and
wherein following conditional expressions are satisfied:
LD/f< 1.00,
0.25< Dpn/LD< 0.50,
1.45< Nd 1 p< 1.62,
30.0<ν d 1 p< 50.0,

0.17< Dpp/LD< 0.50, and
0.15< f 2 p/f< 0.60,

where Nd1p and νd1p are respectively a refractive index and an Abbe number of a material of the positive lens G 1 p , Dpn is a distance on an optical axis between the positive lens G 1 p and the negative lens Gn, LD is a distance on the optical axis from a most object side lens surface of the optical system to an image plane, and f is a focal length of the optical system,
where Dpp is a distance on the optical axis between a positive lens G 2 p located on a most object side among positive lenses arranged on the image side of the positive lens G 1 p and the positive lens G 1 p , and
where ftp is a focal length of the positive lens G 2 p.

2. The optical system according to claim 1 , wherein following conditional expression is satisfied:
0.000<θ gF _ G 1 p− 0.6438+0.001682×ν d 1 p< 0.015,

where θgF_G 1 p is a partial dispersion ratio of the material of the positive lens G 1 p.

3. The optical system according to claim 1 , wherein the positive lens G 1 p has a meniscus shape convex toward the object side.

4. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.30<( R 12− R 11)/( R 12+ R 11)<1.00,

where R11 is a radius of curvature of an object side lens surface of the positive lens G 1 p , and R12 is a radius of curvature of an image side lens surface of the positive lens G 1 p.

5. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.30< f 1 p/f< 1.00,
where f1p is a focal length of the positive lens G 1 p.

6. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
20.0<ν dn< 45.0,

where νdn is an Abbe number of a material of the negative lens Gn.

7. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.65< Ndn< 2.20,
where Ndn is a refractive index of a material of the negative lens Gn.

8. The optical system according to claim 1 , wherein the optical system has a focusing unit that moves during focusing, and wherein the following conditional expression is satisfied:
20.00<Σ(ν dni/fni )/Σ(1 /fni )<45.00,

where νdni is an Abbe number of a material of an i-th negative lens counted from the object side among negative lenses arranged between the positive lens G 1 p and the focusing unit, and fni is a focal length of the i-th negative lens.

9. The optical system according to claim 1 , wherein the following conditional expressions are satisfied:
0.020<θ gF _ G 2 p− 0.6438+0.001682× vd 2 p< 0.100, and

ν d 2 p> 73.0,

where νd2p and θgF_G 2 p are respectively an Abbe number and a partial dispersion ratio of a material of the positive lens G 2 p.

10. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.20< f 2 p/f 1 p< 0.80,
where f1p is a focal length of the positive lens G 1 p , and f2p is a focal length of the positive lens G 2 p.

11. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.22< Dpp/LD< 0.50.

12. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.45< Nd 1 p≤ 1.593.

13. An image pickup apparatus comprising:
an optical system; and
an image pickup element configured to receive an image formed by the optical system,
wherein the optical system includes a positive lens G 1 p , and a negative lens Gn located on a most object side among negative lenses arranged on an image side of the positive lens G 1 p,
wherein the positive lens G 1 p is a positive lens located on a most object side among positive lenses included in the optical system,
wherein the optical system does not include a diffractive optical element, and
wherein following conditional expressions are satisfied:
LD/f< 1.00,
0.25< Dpn/LD< 0.50,
1.45< Nd 1 p< 1.62,
30.0<ν d 1 p< 50.0,

0.17< Dpp/LD< 0.50, and
0.15< f 2 p/f< 0.60,

where Nd1p and νd1p are respectively a refractive index and an Abbe number of a material of the positive lens G 1 p , Dpn is a distance on an optical axis between the positive lens G 1 p and the negative lens Gn, LD is a distance on the optical axis from a most object side lens surface of the optical system to an image plane, and f is a focal length of the optical system,
where Dpp is a distance on the optical axis between a positive lens G 2 p located on a most object side among positive lenses arranged on the image side of the positive lens G 1 p and the positive lens G 1 p , and
where ftp is a focal length of the positive lens G 2 p.

14. The image pickup apparatus according to claim 13 , wherein the following conditional expression is satisfied:
1.45< Nd 1 p≤ 1.593.

Assignees

• Canon Kk

Inventors

• Sugita Shigenobu
• Gyoda Yuichi
• Inoue Suguru

Classifications

• G02B9/26 Primary

  the front and rear components having compound lenses · CPC title

• G02B13/18

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B9/12

  having three components only · CPC title

• G02B13/02

  Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length · CPC title