Optical system and image pickup apparatus

Patent metadata

Field	Value
Publication number	US-10935755-B2
Application number	US-201816051787-A
Country	US
Kind code	B2
Filing date	Aug 1, 2018
Priority date	Aug 7, 2017
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

Provided is an optical system including, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power configured to move during focusing; and a third lens unit. An interval between each pair of adjacent lens units is changed during focusing. The optical system includes an aperture stop. The first lens unit includes at least three positive lenses including a positive lens (G1P) arranged closest to the object side. A distance LD on an optical axis from a lens surface closest to the object side of the optical system to an image plane, a focal length “f” of the optical system, a refractive index ndG1P of a material of the positive lens (G1P), and an Abbe number νdG1P of the material of the positive lens (G1P) are each appropriately set.

First claim

What is claimed is:

1. An optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power configured to move during focusing; and
a third lens unit,
wherein an interval between each pair of adjacent lens units is changed during focusing,
wherein the optical system comprises an aperture stop,
wherein the first lens unit comprises at least three positive lenses including a positive lens G1P arranged closest to the object side and a plurality of negative lenses including a negative lens GIN located closest to the object side among the plurality of negative lenses, and
wherein the conditional expressions:
LD/f< 1.0;
1.58< ndG 1 P< 1.8;
63< νdG 1 P< 75; and
0.17< dPN/f< 0.45,

are satisfied where LD represents a distance on an optical axis from a lens surface closest to the object side of the optical system to an image plane, f represents a focal length of the optical system, ndG1P represents a refractive index of a material of the positive lens G1P, νdG1P represents an Abbe number of the material of the positive lens G1P, and dPN represents a distance on the optical axis from a lens surface on the image side of the positive lens GIP to a lens surface on the object side of the negative lens GIN.

2. The optical system according to claim 1 , wherein the conditional expression:
0.534<θ gFG 1 P< 0.560,

is satisfied where θgFG1P represents a relative partial dispersion of the material of the positive lens G1P.

3. The optical system according to claim 1 , wherein the conditional expression:
0.7<( R 2 G 1 P+R 1 G 1 P )/( R 2 G 1 P−R 1 G 1 P )<5.5,
is satisfied where R1G1P represents a curvature radius of a lens surface on the object side of the positive lens G1P, and R2G1P represents a curvature radius of a lens surface on the image side of the positive lens G1P.

4. The optical system according to claim 1 , wherein the conditional expression:
−2.8< f 1/ f 2<−1.2,

is satisfied where f1 represents a focal length of the first lens unit, and f2 represents a focal length of the second lens unit.

5. The optical system according to claim 1 ,
wherein the conditional expressions:
24<ν dG 1 N< 45; and

0.58<θ gFG 1 N< 0.595,

are satisfied where νdG1N represents an Abbe number of a material of the negative lens G1N, and θgFG1N represents a relative partial dispersion of the material of the negative lens G1N.

6. The optical system according to claim 5 , wherein the conditional expression:
−1.0<( R 2 G 1 N+R 1 G 1 N )/( R 2 G 1 N−R 1 G 1 N )<−0.1,

is satisfied where R1G1N represents a curvature radius of a lens surface on the object side of the negative lens G1N, and R2G1N represents a curvature radius of a lens surface on the image side of the negative lens G1N.

7. The optical system according to claim 5 , wherein the conditional expression:
1.5<| fG 1 P/fG 1 N|< 3.0,
is satisfied where fG1P represents a focal length of the positive lens G1P, and fG1N represents a focal length of the negative lens G1N.

8. The optical system according to claim 1 , wherein the conditional expression:
0.3< f 1/ f< 0.7,
is satisfied where f1 represents a focal length of the first lens unit.

9. The optical system according to claim 1 , wherein the conditional expression:
350< HKG 1 P< 500,
is satisfied where HKG1P represents a Knoop hardness of the positive lens G1P.

10. The optical system according to claim 1 , wherein the conditional expression:
0.2< dF 2/ LD< 0.5,
is satisfied where dF2 represents a distance on the optical axis from a lens surface on the image side of the second lens unit to the image plane.

11. The optical system according to claim 1 , wherein the third lens unit comprises, in order from the object side to the image side:
a first sub-lens unit;
a second sub-lens unit; and
a third sub-lens unit,
wherein the first sub-lens unit and the third sub-lens unit are configured not to move during focusing and correction of image blurring, and
wherein the second sub-lens unit is configured to move in a direction containing a component in a direction perpendicular to the optical axis during correction of image blurring.

12. The optical system according to claim 1 , wherein the optical system consists of a plurality of lens units including the aperture stop, and
wherein the plurality of lens units consist, in order from the object side to the image side, of the first lens unit, the second lens unit, and the third lens unit.

13. The optical system according to claim 12 , wherein the third lens unit is configured not to move during focusing.

14. An image pickup apparatus comprising:
an optical system comprising, in order from an object side to an image side:
a first lens unit having a positive refractive power;
a second lens unit having a negative refractive power configured to move during focusing; and
a third lens unit,
wherein an interval between each pair of adjacent lens units is changed during focusing,
wherein the optical system comprises an aperture stop,
wherein the first lens unit comprises at least three positive lenses including a positive lens G1P arranged closest to the object side and a plurality of negative lenses including a negative lens GIN located closest to the object side among the plurality of negative lenses, and
wherein the conditional expressions:
LD/f< 1.0;
1.58< ndG 1 P< 1.8;
63<ν dG 1 P< 75; and

0.17< dPN/f< 0.45,

are satisfied where LD represents a distance on an optical axis from a lens surface closest to the object side of the optical system to an image plane, f represents a focal length of the optical system, ndG1P represents a refractive index of a material of the positive lens G1P, νdG1P represents an Abbe number of the material of the positive lens G1P, and dPN represents a distance on the optical axis from a lens surface on the image side of the positive lens GIP to a lens surface on the object side of the negative lens GIN; and
an image pickup element configured to receive an image formed by the optical system.

15. An optical system comprising,
an aperture stop, and
three or more positive lenses disposed on an object side of the aperture stop, the three or more positive lenses including a positive lens G1P which is arranged closest to the object side, and
a plurality of negative lenses including a negative lens GIN located closest to the object side among the plurality of negative lenses,
wherein the conditional expressions:
LD/f< 1.0;
1.58< ndG 1 P< 1.8;
63< vdG 1 P< 75; and
0.17< dPN/f< 0.45,

are satisfied where LD represents a distance on an optical axis from a lens surface closest to the object side of the optical system to an image plane, f represents a focal length of the optical system, ndG1P represents a refractive index of a material of the positive lens G1P, vdG1P represents an Abbe number of the material of the positive lens G1P, and dPN represents a distance on the optical axis from a lens surface on the image side of the positive lens GIP to a lens surface on the object side of the negative lens GIN.

16. The optical system according to claim 15 , wherein the conditional expression:
0.534<θ gFG 1 < 0.560,

is satisfied where θgFG1P represents a relative partial dispersion of the material of the positive lens G1P.

17. The optical system according to claim 15 , wherein the conditional expression:
0.7<( R 2 G 1 P+R 1 G 1 P )/( R 2 G 1 P−R 1 G 1 P )<5.5,

Assignees

• Canon Kk

Inventors

• Saito Shinichiro
• Nakahara Makoto

Classifications

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• G02B15/142

  having two groups only · CPC title

• G02B27/0037

  with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876) · CPC title

• G02B27/646

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• G02B9/12 Primary

  having three components only · CPC title