Finder and imaging apparatus

Patent metadata

Field	Value
Publication number	US-9798121-B2
Application number	US-201615224826-A
Country	US
Kind code	B2
Filing date	Aug 1, 2016
Priority date	Aug 25, 2015
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

A finder is a reverse Galileo type finder comprising, in order from the object side to the eye point side: an objective lens group having a negative refractive power; and an eyepiece lens group having a positive refractive power. The distance between the objective lens group and the eyepiece lens group is the longest distance from among distances between lenses, as an air converted length, in an observation optical system from the objective lens group to the eyepiece lens group. The eyepiece lens group consists of, in order from the object side to the eye point side: a first lens having a negative refractive power; a second lens having a positive refractive power; and a third lens having a negative refractive power. The first lens and the third lens are fixed while the second lens moves in the direction of the optical axis during diopter adjustment.

First claim

What is claimed is:

1. A reverse Galileo type finder comprising, in order from the object side to the eye point side:
an objective lens group having a negative refractive power; and
an eyepiece lens group having a positive refractive power;
the distance between the objective lens group and the eyepiece lens group being the longest distance from among distances between lenses, as an air converted length, in an observation optical system from the objective lens group to the eyepiece lens group;
the eyepiece lens group consisting of, in order from the object side to the eye point side: a first lens having a negative refractive power; a second lens having a positive refractive power; and a third lens having a negative refractive power; and
the first lens and the third lens being fixed while the second lens moves in the direction of the optical axis during diopter adjustment.

2. A finder as defined in claim 1 , in which Conditional Formula (1) below is satisfied:
0.05< fN/f 3<0.5  (1)

wherein fN is the focal length of the objective lens group and f3 is the focal length of the third lens.

3. A finder as defined in claim 2 , in which Conditional Formula (1-1) below is satisfied
0.1< fN/f 3<0.4  (1-1).

4. A finder as defined in claim 2 , in which Conditional Formula (1-2) below is satisfied
0.15< fN/f 3<0.36  (1-2).

5. A finder as defined in claim 1 , in which Conditional Formula (2) below is satisfied:
0.55< D/f 2<1.5  (2)

wherein D is the air converted length from the lens surface most toward the eye point side within the objective lens group to the lens surface most toward the object side within the eyepiece lens group, and f2 is the focal length of the second lens.

6. A finder as defined in claim 5 , in which Conditional Formula (2-1below is satisfied:
0.6< D/f 2<1  (2-1).

7. A finder as defined in claim 1 , in which Conditional Formula (3) below is satisfied:
0.1< m·f 1/ f 3<0.8  (3)

wherein m is the angular magnification ratio of the observation optical system in a state in which the diopter is −1, f1 is the focal length of the first lens, and f3 is the focal length of the third lens.

8. A finder as defined in claim 7 , in which Conditional Formula (3-1) below is satisfied:
0.15< m·f 1/ f 3<0.6  (3-1).

9. A finder as defined in claim 1 , further comprising:
another optical system separate from the observation optical system, outside the optical path of the observation optical system; and
an optical path combining member that combines the optical path of the other optical system and the optical path of the observation optical system, provided between the objective lens group and the eyepiece lens group.

10. A finder as defined in claim 9 , wherein:
the other optical system consists of two lenses having positive refractive powers and one lens having a negative refractive power.

11. An imaging apparatus equipped with a finder a defined in claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Saito Hiroki

Classifications

• G02B25/001

  Eyepieces · CPC title

• G02B13/04

  Reversed telephoto objectives · CPC title

• G02B15/15 Primary

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

• G02B27/106 Primary

  for splitting or combining a plurality of identical beams or images, e.g. image replication · CPC title

• G02B15/143101 Primary

  arranged +-- · CPC title