Eyepiece lens, viewfinder optical system and optical apparatus equipped with the same, and method for manufacturing eyepiece lens

Patent metadata

Field	Value
Publication number	US-9753271-B2
Application number	US-201615062078-A
Country	US
Kind code	B2
Filing date	Mar 5, 2016
Priority date	Dec 28, 2011
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

An eyepiece lens (EL) used for a viewfinder optical system (VF) for viewing, using the eyepiece lens (EL), an image formed by an objective lens (OL), an image displayed by a display member, or an object, wherein an antireflection coating ( 101 ) is disposed on at least one surface among the optical surfaces constituting the eyepiece lens (EL), and the antireflection coating ( 101 ) includes at least one layer ( 101 g ) formed by a wet process.

First claim

The invention claimed is:

1. An eyepiece lens comprising, in order from an object along an optical axis,
a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power, wherein
an antireflection coating is disposed on at least one optical surface of the eyepiece lens, and
wherein the following conditional expression is satisfied:
Nn ( ABE )>1.870

where Nn (ABE) denotes an average value of refractive indexes, with respect to d-line, of all lenses having negative refractive power in the first and third lens groups.

2. The eyepiece lens according to claim 1 , wherein at least one of the first lens group, the second lens group and the third lens group is movable along an optical axis to perform diopter adjustment.

3. The eyepiece lens according to claim 1 , wherein the second lens group includes a biconvex lens component.

4. The eyepiece lens according to claim 1 , wherein the third lens group includes a meniscus lens component having a convex surface facing the object.

5. The eyepiece lens according to claim 1 , wherein
the following conditional expression is satisfied:
30.0>ν( ABE )

where ν (ABE) denotes an average value of Abbe numbers, with respect to d-line, of all lenses having negative refractive power in the first and third lens groups.

6. The eyepiece lens according to claim 5 , wherein
the following conditional expression is satisfied:
ν2>40

where ν2 denotes an average value of Abbe numbers, with respect to d-line, of all lenses in the second lens group.

7. The eyepiece lens according to claim 1 , wherein
at least one optical surface of the second lens group is aspherical.

8. The eyepiece lens according to claim 1 , wherein
the following conditional expression is satisfied:
S 3>2.4

where S3 denotes a shape factor of a lens component located closest to an eye point in the third lens group, which is a value defined by (Ro 3 +Re 3 )/(Ro 3 −Re 3 ), where Ro 3 denotes a radius of curvature of an object side surface of the lens component, and Re 3 denotes a radius of curvature of the eye point side surface of the lens component.

9. The eyepiece lens according to claim 1 , wherein
the second lens group is movable along an optical axis to perform diopter adjustment.

10. The eyepiece lens according to claim 1 , wherein
the antireflection coating is a multilayer film, and at least one of the layers satisfies the following conditional expression:
nd≦ 1.30

where nd denotes a refractive index with respect to d-line.

11. The eyepiece lens according to claim 10 , wherein
an outermost surface layer constituting the multilayer film satisfies the conditional expression:
nd≦ 1.30.

12. The eyepiece lens according to claim 10 , wherein
said one optical surface on which the antireflection coating is formed is a lens surface which is concave as viewed from an eye point.

13. The eyepiece lens according to claim 12 , wherein
the lens surface which is concave viewed from the eye point is a lens surface closest to the object among the optical surfaces of the first, second, and third lens groups.

14. The eyepiece lens according to claim 12 , wherein
the lens surface which is concave viewed from the eye point is a lens surface closest to an image plane among the optical surfaces of the first, second, and third lens groups.

15. The eyepiece lens according to claim 10 , wherein
said one optical surface on which the antireflection coating is formed is a lens surface which is concave as viewed from an object.

16. The eyepiece lens according to claim 15 , wherein
the concave lens surface on which the antireflection coating is formed is a lens surface closest to an image plane among the optical surfaces of the second lens group.

17. The eyepiece lens according to claim 10 , wherein
said one optical surface on which the antireflection coating is formed is an optical surface other than an optical surface closest to an eye point.

18. A viewfinder optical system for viewing an image formed by an objective lens, comprising the eyepiece lens according to claim 1 .

19. An optical apparatus, comprising the viewfinder optical system according to claim 18 .

20. A method for manufacturing an eyepiece lens comprising:
constructing the eyepiece lens to include, in order from an object along an optical axis, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power;
disposing an antireflection coating, which includes at least one layer formed by a wet process, on at least one optical surface of the eyepiece lens; and
disposing a lens having said one optical surface on which the antireflection coating is formed, in a lens barrel, and
wherein the eyepiece lens is constructed such that the following conditional expression is satisfied:
Nn ( ABE )>1.870

where Nn (ABE) denotes an average value of refractive indexes, with respect to d-line, of all lenses having negative refractive power in the first and third lens groups.

21. The method for manufacturing an eyepiece lens according to claim 20 , wherein
the following conditional expression is satisfied:
nd≦ 1.30

where nd denotes a refractive index, with respect to d-line, of said one layer formed by the wet process.

22. The method for manufacturing an eyepiece lens according to claim 20 , wherein
said one optical surface on which the antireflection coating is formed is a lens surface which is concave as viewed from an eye point.

Assignees

• Nikon Corp

Inventors

• Tanaka Issei
• Harada Hiroki
• Matsuo Taku

Classifications

• G02B23/14

  Viewfinders (for photographic apparatus G03B13/02) · CPC title

• G03B13/06

  with lenses with or without reflectors · CPC title

• G02B9/56

  all components being simple lenses · CPC title

• G02B27/0018

  with means for preventing ghost images (anti-reflection coatings G02B1/11) · CPC title

• G02B9/12

  having three components only · CPC title