Optical system and image pickup apparatus

Patent metadata

Field	Value
Publication number	US-12345857-B2
Application number	US-202217744823-A
Country	US
Kind code	B2
Filing date	May 16, 2022
Priority date	May 20, 2021
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

An optical system consists of a front unit and a rear unit. The front unit consists of a first lens having a positive refractive power, a second lens disposed on an image side of the first lens and having a positive refractive power, and a third lens. Each of the first lens and the second lens has a refractive index of 1.7 or higher for d-line. The rear unit consists of two or more and four or fewer lenses and includes a fourth lens having a positive refractive power and a fifth lens adjacent to the fourth lens and having a negative refractive power. Each of the fourth lens and the fifth lens is made of an organic material. A predetermined condition is satisfied.

First claim

What is claimed is:

1. An optical system consisting of a front unit and a rear unit,
wherein the front unit consists of:
a first lens having a positive refractive power;
a second lens disposed on an image side of the first lens and having a positive refractive power; and
a third lens,
wherein each of the first lens and the second lens has a refractive index of 1.7 or higher for d-line,
wherein the rear unit consists of two or more and four or fewer lenses and includes a fourth lens having a positive refractive power and a fifth lens adjacent to the fourth lens and having a negative refractive power,
wherein each of the fourth lens and the fifth lens is made of an organic material, and
wherein the following inequalities are satisfied:
0.75<ν dA/νdB< 1.30

0.75<− fA/fB< 1.30

0.50< du/BF< 1.50

where νdA is an Abbe number of the fourth lens, νdB is an Abbe number of the fifth lens, fA is a focal length of the fourth lens, fB is a focal length of the fifth lens, du is an on-axis distance from a surface vertex closest to an object to a surface vertex closest to an image plane of the rear unit, and BF is a backfocus of the optical system.

2. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
α p 1<100×10{circumflex over ( )}−7

where αp1 is a linear expansion coefficient (/° C.) of the first lens.

3. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
25<ν dp 1<60

where νdp1 is an Abbe number of the first lens.

4. The optical system according to claim 1 , wherein the following inequalitys expression is satisfied:
α p 2<100×10{circumflex over ( )}−7

where αp2 is a linear expansion coefficient (/° C.) of the second lens.

5. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
25<ν dp 2<60

where νdp2 is an Abbe number of the second lens.

6. The optical system according to claim 1 , wherein the third lens has a negative refractive power.

7. The optical system according to claim 6 , wherein the following inequalitys is satisfied:
α n< 100×10{circumflex over ( )}−7

where αn is a linear expansion coefficient (/° C.) of the third lens.

8. The optical system according to claim 6 , wherein the following inequalitys is satisfied:
1.60< N< 2.10

where N is a refractive index of the third lens.

9. The optical system according to claim 6 , wherein the following inequalitys is satisfied:
15<ν dn <35

where νdn is an Abbe number of the third lens.

10. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
1.4< fA/f< 3.5

where f is a focal length of the optical system.

11. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
1.00< f/BF< 3.00

where f is a focal length of the optical system, and BF is a backfocus of the optical system.

12. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
0.5<| Fu|/Fm< 25.0

where Fm is a focal length of the front unit, and Fu is a focal length of the rear unit.

13. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
0.10< dA/BF< 0.60

where dA is an on-axis thickness of the fourth lens.

14. The optical system according to claim 1 , wherein the following inequalitys is satisfied:
0.05< dB/BF< 0.40

where dB is an on-axis thickness of the fifth lens, and BF is a backfocus of the optical system.

15. The optical system according to claim 1 , wherein the following inequalitys are satisfied:
50<ν dA< 60

1.45< NA< 1.60

where NA is a refractive index of the fourth lens.

16. The optical system according to claim 1 , wherein the following inequalitys are satisfied:
15<ν dA< 40

1.55< NA< 1.75

where NA is a refractive index of the fourth lens.

17. The optical system according to claim 6 , wherein the following inequalitys is satisfied:
0.20<− fn/f< 0.70

where f is a focal length of the optical system, and fn is a focal length of the third lens.

18. The optical system according to claim 1 , wherein the first lens is disposed closest to an object.

19. The optical system according to claim 1 , wherein the front unit consists of, in order from an object side to the image side, the first lens, the third lens having a negative refractive power, and the second lens.

20. An image pickup apparatus comprising:
an optical system; and
an image sensor configured to image an optical image formed by the optical system,
wherein the optical system consists of a front unit and a rear unit,
wherein the front unit consists of:
a first lens having a positive refractive power;
a second lens disposed on an image side of the first lens and having a positive refractive power; and
a third lens,
wherein each of the first lens and the second lens has a refractive index of 1.7 or higher for d-line,
wherein the rear unit consists of two or more and four or fewer lenses and includes a fourth lens having a positive refractive power and a fifth lens adjacent to the fourth lens and having a negative refractive power,
wherein each of the fourth lens and the fifth lens is made of an organic material, and
wherein the following inequalities are satisfied:
0.75<ν dA/νdB< 1.30

0.75<− fA/fB< 1.30

0.50< du/BF< 1.50

where νdA is an Abbe number of the fourth lens, νdB is an Abbe number of the fifth lens, fA is a focal length of the fourth lens, fB is a focal length of the fifth lens, du is an on-axis distance from a surface vertex closest to an object to a surface vertex closest to an image plane of the rear unit, and BF is a backfocus of the optical system.

Assignees

• Canon Kk

Inventors

• Ebe Hiroki
• Saito Shinichiro

Classifications

• G02B13/0015 Primary

  characterised by the lens design · CPC title

• G02B9/60

  having five components only · CPC title

• G02B1/041

  Lenses · CPC title

• G02B13/0045 Primary

  having five or more lenses · CPC title