Optical system, optical apparatus, and method for manufacturing the optical system

Patent metadata

Field	Value
Publication number	US-9915803-B2
Application number	US-201414426755-A
Country	US
Kind code	B2
Filing date	Feb 14, 2014
Priority date	Feb 19, 2013
Publication date	Mar 13, 2018
Grant date	Mar 13, 2018

Abstract

The present invention has, in order from an object: a first lens (L 1 ) having negative refractive power; a second lens (L 2 ), which is a positive meniscus lens having a convex surface facing the object; an aperture stop (S); and a third lens (L 3 ) having a convex surface facing the object, and satisfies the following conditional expression (1):

6.6<| f 12 /f|   (1)
where f12 denotes a composite focal length of the first lens (L 1 ) and the second lens (L 2 ), and f denotes a focal length of the optical system (WL).

First claim

The invention claimed is:

1. An optical system, comprising, in order from an object:
a first lens having negative refractive power;
a second lens, being a positive single meniscus lens and having a convex surface facing the object;
an aperture stop; and
a third lens having a convex surface facing the object, the following conditional expression being satisfied:
6.6<| f 12/ f|

where
f12 denotes a composite focal length of the first lens and the second lens, and
f denotes a focal length of the optical system, and the following conditional expression being satisfied:
0.75<{(− f 1)/ d}/f< 1.20

where
f1 denotes a focal length of the first lens, and
d denotes a distance on an optical axis from an object side surface of the first lens to an image side surface of a lens located closest to the image.

2. The optical system according to claim 1 , wherein the first lens is a negative meniscus lens having a concave surface facing the image.

3. The optical system according to claim 1 , wherein the third lens has positive refractive power.

4. The optical system according to claim 1 , wherein the image side surface of the lens located closest to the image is aspherical.

5. The optical system according to claim 1 , wherein the first lens, the second lens and the third lens are all spherical lenses.

6. An optical apparatus, which includes the optical system according to claim 1 .

7. A method for manufacturing an optical system, including, in order from an object, a first lens having negative refractive power, a second lens, being a positive single meniscus lens and having a convex surface facing the object, an aperture stop, and a third lens having a convex surface facing the object,
the method including: assembling each lens in a lens barrel so as to satisfy the following expression:
6.6<| f 12/ f|

where
f12 denotes a composite focal length of the first lens and the second lens, and
f denotes a focal length of the optical system, and so as to satisfy the following expression:
0.75<{(− f 1)/ d}f< 1.20

where
f1 denotes a focal length of the first lens, and
d denotes a distance on an optical axis from an object side surface of the first lens to an image side surface of a lens located closest to the image.

8. An optical system, comprising, in order from an object:
a first lens having negative refractive power;
a second lens, being a positive single meniscus lens and having a convex surface facing the object;
an aperture stop; and
a third lens having positive refractive power and having a convex surface facing the object, the following conditional expression being satisfied:
6.6<| f 12/ f|

where
f12 denotes a composite focal length of the first lens and the second lens, and
f denotes a focal length of the optical system.

9. A method for manufacturing an optical system, including, in order from an object, a first lens having negative refractive power, a second lens, being a positive single meniscus lens and having a convex surface facing the object, an aperture stop, and a third lens having positive refractive power and having a convex surface facing the object,
the method including: assembling each lens in a lens barrel so as to satisfy the following expression:
6.6<| f 12/ f|

where
f12 denotes a composite focal length of the first lens and the second lens, and
f denotes a focal length of the optical system.

Assignees

• Nikon Corp

Inventors

• Suzuki Atsushi

Classifications

• G02B13/005

  having spherical lenses only · CPC title

• G02B13/18

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• Y10T29/49826

  Assembling or joining · CPC title

• G02B9/12 Primary

  having three components only · CPC title

• G02B15/177

  having a negative front lens or group of lenses · CPC title