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US 11,448,856 B2Granted
Converter lens, interchangeable lens, and image pickup apparatus
AssigneeCanon Kabushiki Kaisha
InventorShinya Okuoka
Life of this patent
Estimating the term…
Abstract
A converter lens includes three or more negative lenses and increases the focal length of an entire system, in which an average refractive index Ndave at the d-line (wavelength of 587.56 nm) of a material of all the negative lenses included in the converter lens is defined.
Claims17
A converter lens which has a negative refractive power and increases a focal length of an entire system when arranged on an image side of a master lens, the converter lens consisting of:
- a first lens unit having positive refractive power;
- and
- a second lens unit having negative refractive power and arranged on an image side of the first lens unit,
- wherein the first lens unit consists of a negative lens and a first positive lens,
- wherein the second lens unit including a second positive lens arranged closest to an image side of the converter lens,
- wherein three or more negative lenses are included in the converter lens, and
- wherein the following inequalities are satisfied:
- 1.92<Ndave<2.10, and
- 1.30<(R1+R2)/(R1−R2)<2.50,
- where Ndave represents an average refractive index at a d-line of a material of all negative lenses included in the converter lens, R1 represents a curvature radius of a surface of the second positive lens on an object side, and R2 represents a curvature radius of a surface of the second positive lens on the image side.
7 more elements
An interchangeable lens comprising:
- a master lens;
- and
- a converter lens which has a negative refractive power and increases a focal length of an entire system when arranged on an image side of the master lens,
- wherein the converter lens consists of
- a first lens unit having positive refractive power and
- second lens unit having negative refractive power and arranged on an image side of the first lens unit,
- wherein the first lens unit consists of a negative lens and a first positive lens,
- wherein the second lens unit including a second positive lens arranged closest to an image side of the converter lens,
- wherein three or more negative lenses are included in the converter lens, and
- wherein the following inequalities are satisfied:
- 1.92<Ndave<2.10, and
- 1.30<(R1+R2)/(R1−R2)<2.50,
- where Ndave represents an average refractive index at the d-line of a material of all negative lenses included in the converter lens, R1 represents a curvature radius of a surface of the second positive lens on an object side, and R2 represents a curvature radius of a surface of the second positive lens on the image side.
10 more elements
An apparatus comprising:
- a master lens;
- a converter lens which has a negative refractive power and increases a focal length of an entire system when arranged on an image side of the master lens;
- and
- an imaging device configured to receive an image formed by the master lens and the converter lens,
- wherein the converter lens consists of
- a first lens unit having positive refractive power and
- second lens unit having negative refractive power and arranged on an image side of the first lens unit,
- wherein the first lens unit consists of a negative lens and a first positive lens,
- wherein the second lens unit uncluding a second positive lens arranged closest to an image side of the converter lens,
- wherein three or more negative lenses are included in the converter lens, and
- wherein the following inequalities are satisfied:
- 1.92<Ndave<2.10, and
- 1.30<(R1+R2)/(R1−R2)<2.50,
- where Ndave represents an average refractive index at the d-line of a material of all negative lenses included in the converter lens, R1 represents a curvature radius of a surface of the second positive lens on an object side, and R2 represents a curvature radius of a surface of the second positive lens on the image side.
11 more elements
Dependencies are inferred from the claim text.