Eyepiece lens, observation optical system, and optical apparatus

Patent metadata

Field	Value
Publication number	US-2021199947-A1
Application number	US-202017116205-A
Country	US
Kind code	A1
Filing date	Dec 9, 2020
Priority date	Dec 25, 2019
Publication date	Jul 1, 2021
Grant date	—

Abstract

The eyepiece lens consists of, in order from an observation object side to an eye point side, a positive first lens, a negative second lens, a positive third lens, and a positive fourth lens. All lenses are single lenses. The second lens has a biconcave shape. An observation object-side surface of the fourth lens has a convex shape. In a case where a refractive index of the third lens with respect to d line is N3, the eyepiece lens satisfies the following conditional expression.1.76<N3<2

First claim

What is claimed is:

1 . An eyepiece lens consisting of, in order from an observation object side to an eye point side:
a first lens having a positive refractive power; a second lens having a negative refractive power; a third lens having a positive refractive power; and a fourth lens having a positive refractive power, wherein the first lens, the second lens, the third lens, and the fourth lens are all single lenses, the second lens has a biconcave shape, an observation object-side surface of the fourth lens has a convex shape, and in a case where a refractive index of the third lens with respect to d line is N3, a conditional expression (1) is satisfied
1.76< N 3<2  (1).

2 . The eyepiece lens according to claim 1 ,
wherein, in a case where a focal length of the second lens is f2, and a focal length of the fourth lens is f4, a conditional expression (2) is satisfied
−0.42< f 2/ f 4<−0.2  (2).

3 . The eyepiece lens according to claim 1 ,
wherein, in a case where a focal length of the eyepiece lens is f, and a focal length of the first lens is f1, a conditional expression (3) is satisfied
1.2< f/f 1<3.5  (3).

4 . The eyepiece lens according to claim 1 ,
wherein, in a case where a focal length of the first lens is f1, and a focal length of the fourth lens is f4, a conditional expression (4) is satisfied
2.7< f 4/ f 1<8  (4).

5 . The eyepiece lens according to claim 1 ,
wherein, in a case where a radius of curvature of an eye point-side surface of the second lens is R2r, and a radius of curvature of an observation object-side surface of the third lens is R3f, a conditional expression (5) is satisfied
−2.1<( R 2 r+R 3 f )/( R 2 r−R 3 f )<−0.2  (5).

6 . The eyepiece lens according to claim 1 ,
wherein the first lens has a biconvex shape.

7 . The eyepiece lens according to claim 1 ,
wherein an eye point-side surface of the third lens has a convex shape.

8 . The eyepiece lens according to claim 1 ,
wherein the observation object-side surface of the fourth lens has an aspheric surface.

9 . The eyepiece lens according to claim 1 ,
wherein an eye point-side surface of the second lens has an aspheric surface.

10 . The eyepiece lens according to claim 1 ,
wherein diopter adjustment is performed by changing a distance between an observation object and the eyepiece lens in a direction of an optical axis.

11 . The eyepiece lens according to claim 1 ,
wherein a conditional expression (1-1) is satisfied
1.8< N 3<1.9  (1-1).

12 . The eyepiece lens according to claim 2 ,
wherein a conditional expression (2-1) is satisfied
−0.35< f 2/ f 4<−0.21  (2-1).

13 . The eyepiece lens according to claim 3 ,
wherein a conditional expression (3-1) is satisfied
1.4< f/f 1<2.5  (3-1).

14 . The eyepiece lens according to claim 4 ,
wherein a conditional expression (4-1) is satisfied
3< f 4/ f 1<5  (4-1).

15 . The eyepiece lens according to claim 5 ,
wherein a conditional expression (5-1) is satisfied
−1.75<( R 2 r+R 3 f )/( R 2 r−R 3 f )<−0.6  (5-1).

16 . An observation optical system comprising:
a display element; and the eyepiece lens according to claim 1 , wherein the observation optical system allows observation of an image of the display element through the eyepiece lens, and during diopter adjustment, the eyepiece lens remains stationary, and the display element is moved by changing a distance between the display element and the eyepiece lens in a direction of an optical axis.

17 . An observation optical system comprising:
a display element; and a lens group consisting of a plurality of lenses, wherein the observation optical system allows observation of an image of the display element through the lens group, during diopter adjustment, the lens group remains stationary, and the display element is moved by changing a distance between the display element and the lens group in a direction of an optical axis, and in a case where a refractive index of at least one lens of the lens group with respect to d line is Nx, a conditional expression (6) is satisfied
1.76< Nx< 2  (6).

18 . The observation optical system according to claim 17 ,
wherein the lens group consists of four lenses, and a lens satisfying the conditional expression (6) is a third lens from a side of the display element among the four lenses.

19 . An optical apparatus comprising:
the eyepiece lens according to claim 1 .

20 . An optical apparatus comprising:
the observation optical system according to claim 16 .

Assignees

• Fujifilm Corp

Inventors

• Saito Hiroki

Classifications

• G02B25/001 Primary

  Eyepieces · CPC title

• G02B25/04

  affording a wide-angle view, e.g. through a spy-hole · CPC title

• G02B9/34

  having four components only · CPC title

• G02B13/04

  Reversed telephoto objectives · CPC title