Converter lens, interchangeable lens, and image capturing apparatus

Patent metadata

Field	Value
Publication number	US-2023341663-A1
Application number	US-202318343184-A
Country	US
Kind code	A1
Filing date	Jun 28, 2023
Priority date	Feb 27, 2019
Publication date	Oct 26, 2023
Grant date	—

Abstract

A converter lens according to an exemplary embodiment of the present invention is a converter lens that has a negative refractive power and increases a focal length of an entire system. The converter lens includes a front group having a positive refractive power and a rear group having a negative refractive power, and the front group is a lens unit having a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by combining a refractive power of each lens in order from the lens closest to an object toward an image side. At this time, a focal length of the front group, a focal length of the converter lens, and a lateral magnification of the converter lens when the converter lens is disposed on an image side of a master lens are determined as appropriate.

First claim

What is claimed is:

1 . A converter lens that has a negative refractive power as a whole and is disposed on an image side of a master lens so that a focal length of an entire system becomes longer than a focal length of the master lens alone,
wherein the converter lens consists of a front unit having a positive refractive power and a rear unit having a negative refractive power, wherein the front unit has a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by a refractive power of each lens being combined in order from the lens closest to an object to an image side, wherein the rear unit has a positive lens closest to an image side and a negative lens next to the positive lens, wherein an object side surface or an image side surface of the negative lens is a cemented surface, and wherein the following conditional expression is satisfied:
1.00< L /( sk ×β)<4.00

where L is a distance on an optical axis from a lens surface closest to the object in the converter lens to a lens surface closest to the image plane in the converter lens, and sk is a distance on the optical axis from a lens surface closest to the image plane in the converter lens to the image plane when the converter lens is disposed on an image side of the master lens.

2 . An interchangeable lens including a master lens and a converter lens that has a negative refractive power as a whole and is disposed in an optical path so that a focal length of an entire system becomes longer than a focal length of the master lens alone,
wherein the converter lens consists of a front unit having a positive refractive power and a rear unit having a negative refractive power, wherein the front unit has a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by a refractive power of each lens being combined in order from the lens closest to an object to an image side, wherein the rear unit has a positive lens closest to an image side and a negative lens next to the positive lens, wherein an object side surface or an image side surface of the negative lens is a cemented surface, and wherein the following conditional expression is satisfied:
1.00< L /( sk ×β)<4.00

where L is a distance on an optical axis from a lens surface closest to the object in the converter lens to a lens surface closest to the image plane in the converter lens, and sk is a distance on the optical axis from a lens surface closest to the image plane in the converter lens to the image plane when the converter lens is disposed on an image side of the master lens.

3 . An image capturing apparatus including a master lens, a converter lens that collectively has a negative refractive power and is in an optical path so that a focal length of an entire system becomes longer than a focal length of the master lens alone, and an image sensor,
wherein the converter lens consists of a front unit having a positive refractive power and a rear unit having a negative refractive power, wherein the front unit has a combined refractive power having a maximum positive refractive power in a case where the combined refractive power is obtained by a refractive power of each lens being combined in order from the lens closest to an object to an image side, wherein the rear unit has a positive lens closest to an image side and a negative lens next to the positive lens, wherein an object side surface or an image side surface of the negative lens is a cemented surface, and wherein the following conditional expression is satisfied:
1.00< L /( sk ×β)<4.00

where L is a distance on an optical axis from a lens surface closest to the object in the converter lens to a lens surface closest to the image plane in the converter lens, and sk is a distance on the optical axis from a lens surface closest to the image plane in the converter lens to the image plane when the converter lens is disposed on an image side of the master lens.

Assignees

• Canon Kk

Inventors

• Ebe Hiroki
• Saito Shinichiro

Classifications

• G02B13/16 Primary

  for use in conjunction with image converters or intensifiers {, or for use with projectors, e.g. objectives for projection TV} · CPC title

• G02B9/10

  one + and one - component · CPC title

• G02B15/10 Primary

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

• G02B15/1421 Primary

  the first group being positive · CPC title

• G02B13/0015

  characterised by the lens design · CPC title