Reduction optical system and image pickup apparatus

Patent metadata

Field	Value
Publication number	US-11914121-B2
Application number	US-202117224764-A
Country	US
Kind code	B2
Filing date	Apr 7, 2021
Priority date	Apr 13, 2020
Publication date	Feb 27, 2024
Grant date	Feb 27, 2024

Abstract

A reduction optical system disposed on an image side of a main optical system, a composite focal length of the main optical system and the reduction optical system being shorter than a focal length of the main optical system, includes a first lens element disposed closest to an object side and having a positive refractive power, a second lens element disposed closest to an image side and having a positive refractive power, and a positive lens and a negative lens disposed between the first lens element and the second lens element.

First claim

What is claimed is:

1. A reduction optical system disposed on an image side of a main optical system, a composite focal length of the main optical system and the reduction optical system being shorter than a focal length of the main optical system, the reduction optical system comprising:
a first lens element disposed closest to an object side and having a positive refractive power;
a second lens element disposed closest to an image side and having a positive refractive power; and
a positive lens and a negative lens disposed between the first lens element and the second lens element,
wherein following conditional expressions are satisfied:
0.440≤ fp 1/ f< 1.500, and

0.600< fp 1/ fp 2<2.500,

where fp1 is a focal length of the first lens element, f is a focal length of the reduction optical system, and fp2 is a focal length of the second lens element.

2. The reduction optical system according to claim 1 , wherein the reduction optical system includes a first positive lens which satisfies following conditional expressions:
1.895< Nph , and
0.200< fph/f< 1.500,
where Nph is a refractive index of the first positive lens, and fph is a focal length of the first positive lens.

3. The reduction optical system according to claim 1 , wherein the first lens element is a single lens, and a following conditional expression is satisfied:
−0.700< fn/f<− 0.100,

where fn is a focal length of a negative lens, included in the reduction optical system, disposed closest to the object side.

4. The reduction optical system according to claim 3 , wherein a following conditional expression is satisfied:
−1.500< f/r 1<−0.200,

where r1 is a radius of curvature of a surface on an object side of the negative lens disposed closest to the object side.

5. The reduction optical system according to claim 1 , wherein a lens disposed closest to the image side included in the second lens element is a positive lens.

6. The reduction optical system according to claim 1 , wherein a following conditional expression is satisfied:
0.500<β<0.900,

where β is a lateral magnification of the reduction optical system disposed on the image side of the main optical system.

7. An image pickup apparatus comprising:
a reduction optical system disposed on an image side of a main optical system, a composite focal length of the main optical system and the reduction optical system being shorter than a focal length of the main optical system; and
an image pickup element configured to pick up an image formed via the reduction optical system,
wherein the reduction optical system comprises:
a first lens element disposed closest to an object side and having a positive refractive power;
a second lens element disposed closest to an image side and having a positive refractive power; and
a positive lens and a negative lens disposed between the first lens element and the second lens element, and
wherein following conditional expressions are satisfied:
0.440≤ fp 1/ f< 1.500, and

0.600< fp 1/ fp 2<2.500,

where fp1 is a focal length of the first lens element, f is a focal length of the reduction optical system, and fp2 is a focal length of the second lens element.

8. A reduction optical system disposed on an image side of a main optical system, a composite focal length of the main optical system and the reduction optical system being shorter than a focal length of the main optical system, the reduction optical system comprising:
a first lens element disposed closest to an object side and having a positive refractive power;
a second lens element disposed closest to an image side and having a positive refractive power; and
a positive lens and a negative lens disposed between the first lens element and the second lens element,
wherein following conditional expression is satisfied:
0.440≤ fp 1/ f< 1.500,

where fp1 is a focal length of the first lens element, and f is a focal length of the reduction optical system, and
wherein the reduction optical system includes a first positive lens which satisfies following conditional expressions:
1.900≤ Nph

where Nph is a refractive index of the first positive lens.

9. The reduction optical system according to claim 8 , wherein a following conditional expression is satisfied:
0.500< fp 1/ fp 2<2.500,
where fp2 is a focal length of the second lens element.

10. The reduction optical system according to claim 8 , wherein a following conditional expression is satisfied:
0.200< fph/f< 1.500,
where fph is a focal length of the first positive lens.

11. The reduction optical system according to claim 8 , wherein the first lens element is a single lens, and a following conditional expression is satisfied:
−0.700< fn/f<− 0.100,

where fn is a focal length of a negative lens, included in the reduction optical system, disposed closest to the object side.

12. The reduction optical system according to claim 11 , wherein a following conditional expression is satisfied:
−1.500< f/r 1<−0.200,

where r1 is a radius of curvature of a surface on an object side of the negative lens disposed closest to the object side.

13. The reduction optical system according to claim 8 , wherein a lens disposed closest to the image side included in the second lens element is a positive lens.

14. The reduction optical system according to claim 8 , wherein a following conditional expression is satisfied:
0.500<β<0.900,

where β is a lateral magnification of the reduction optical system disposed on the image side of the main optical system.

Assignees

• Canon Kk

Inventors

• Shimomura Kazuya
• Yuki Akihiko

Classifications

• G02B15/10 Primary

  by adding a part, e.g. close-up attachment · CPC title

• G02B3/04

  with continuous faces that are rotationally symmetrical but deviate from a true sphere {, e.g. so called "aspheric" lenses} · CPC title

• G02B15/15

  compensation by means of only one movement or by means of only linearly related movements, e.g. optical compensation · CPC title

• G02B13/00 Primary

  Optical objectives specially designed for the purposes specified below (with variable magnification {in general} G02B15/00) · CPC title

• G02B15/08 Primary

  by changing the rear part · CPC title