Optical system and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-10429609-B2
Application number	US-201715607140-A
Country	US
Kind code	B2
Filing date	May 26, 2017
Priority date	Jun 1, 2016
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

In an optical system which includes a positive lens Gp and in which a distance on an optical axis from an object-side lens surface of a lens disposed closest to an object side to an image surface is shorter than a focal length of an entire system, an arrangement and a material of the positive lens Gp, and an arrangement of a focus unit are set appropriately.

First claim

What is claimed is:

1. An optical system comprising:
a positive lens Gp; and
a focus unit configured to move during focusing and disposed closer to an image side than the positive lens Gp,
wherein a front unit disposed closer to an object side than the positive lens Gp has positive refractive power as a whole, and
wherein the following conditional expressions are satisfied:
LD/f <1.00;
15.0<νdGp<24.0;

0.020 <θgF _ Gp− 0.6438+0.001682 ×νdGp <0.100;
0.35< Dpi/LD< 0.80; and
0.05<( R 12 −R 11)/( R 12 +R 11)<0.80,

where νdGp is an Abbe number of a material for the positive lens Gp, θgF_Gp is a partial dispersion ratio of the material for the positive lens Gp, Dpi is a distance on an optical axis from an object-side lens surface of the positive lens Gp to an image surface, LD is a distance on the optical axis from a lens surface of the optical system closest to the object to the image surface, f is a focal length of the optical system, R 11 is curvature radius of the object-side lens surface of the positive lens Gp, and R 12 is a curvature radius of an image-side lens surface of the positive lens Gp.

2. The optical system according to claim 1 , wherein, the following conditional expression is satisfied:
0.30 <fp/f <1.50

where fp is a focal length of the positive lens Gp.

3. The optical system according to claim 1 ,
wherein the front unit includes a negative lens Gn, and wherein the following conditional expression is satisfied:
20.0<νdGn<45.0

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

4. The optical system according to claim 3 , wherein the negative lens Gn has a biconcave shape.

5. The optical system according to claim 3 , wherein the negative lens Gn is a negative lens disposed closest to the object side among the negative lenses included in the optical system.

6. The optical system according to claim 3 , wherein the following conditional expression is satisfied:
0.015 <Dnp/LD <0.20
where Dnp is a distance on the optical axis between an image-side lens surface of the negative lens Gn and an object-side lens surface of the positive lens Gp.

7. The optical system according to claim 3 , wherein the following conditional expression is satisfied:
0.05<− fn/f< 0.30

where fn is a focal length of the negative lens Gn.

8. The optical system according to claim 3 , wherein the following conditional expression is satisfied:
0.10 <−fn/fp <0.60
where fp is a focal length of the positive lens Gp, and fn is a focal length of the negative lens Gn.

9. The optical system according to claim 1 , wherein the front unit includes a positive lens Gfp which satisfies the following conditional expressions:
73.0<νdGfp;

and
0.030 <θgF _ Gfp− 0.6438+0.001682 ×νdGfp <0.100

where νdGfp is an Abbe number of a material for the positive lens Gfp, and θgF_Gfp is a partial dispersion ratio of the material for the positive lens Gfp.

10. The optical system according to claim 9 , wherein, the positive lens Gfp is disposed second closest to the object side among positive lenses included in the front unit; and
wherein the following conditional expression is satisfied:
0.01 <Dpp/LD <0.20

where Dpp is a distance on the optical axis between an image-side lens surface of the positive lens Gfp and an object-side lens surface of the positive lens Gp.

11. The optical system according to claim 9 , wherein the following conditional expression is satisfied:
0.15 <ffp/f <0.60

where ffp is a focal length of the positive lens Gfp.

12. The optical system according to claim 9 , wherein the following conditional expression is satisfied:
0.20 <ffp/fp <1.50

where ffp is a focal length of the positive lens Gfp and fp is a focal length of the positive lens Gp.

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 including a positive lens Gp and a focus unit disposed closer to an image side than the positive lens Gp,
wherein the focus unit is configured to move during focusing,
wherein a front unit disposed closer to an object side than the positive lens Gp has positive refractive power as a whole, and
wherein the following conditional expressions are satisfied:
LD/f <1.00;
15.0<νdGp<24.0;

0.020 <θgF _ Gp− 0.6438+0.001682 ×νdGp <0.100;
0.35 <Dpi/LD <0.80; and
0.05<( R 12− R 11)/( R 12+ R 11)<0.80,

where νdGp is an Abbe number of a material for the positive lens Gp, θgF_Gp is a partial dispersion ratio of the material for the positive lens Gp, Dpi is a distance on an optical axis from an object-side lens surface of the positive lens Gp to an image surface, LD is a distance on the optical axis from a lens surface of the optical system closest to the object to the image surface, f is a focal length of the optical system, R 11 is curvature radius of the object-side lens surface of the positive lens Gp, and R 12 is a curvature radius of an image-side lens surface of the positive lens Gp.

Assignees

• Canon Kk

Inventors

• Sugita Shigenobu
• Inoue Suguru

Classifications

• G02B15/14 Primary

  by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective · CPC title

• G02B13/16

  for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} · CPC title

• G02B27/0025

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

• G02B9/10 Primary

  one + and one - component · CPC title