Zoom lens and image pickup apparatus including the same

Patent metadata

Field	Value
Publication number	US-2016306147-A1
Application number	US-201615094414-A
Country	US
Kind code	A1
Filing date	Apr 8, 2016
Priority date	Apr 16, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

Provided is a zoom lens, including: a negative first lens unit; an aperture stop; and a positive second lens unit, in which the first and second lens units are configured to move so that an interval between the first and second lens units is changed in an optical axis direction, in which the second lens unit includes a positive lens and a negative lens, and in which, when refractive indices of a material with respect to a wavelengths of 400 nm, 1,050 nm and 1,700 nm are respectively represented by Ns, Nm and Nl, and a relative partial dispersion θ of the material is expressed as: θ=(Ns−Nm)/(Ns−Nl), an average value θIR(G 2 p ) AVE of relative partial dispersions of materials of the positive lens in the second lens unit, and an average value θIR(G 2 n ) AVE of relative partial dispersions of materials of the negative lens in the second lens unit are appropriately set.

First claim

What is claimed is:

1 . A zoom lens, comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power; an aperture stop; and a second lens unit having a positive refractive power, wherein the first lens unit and the second lens unit are configured to move during zooming so that an interval between each pair of adjacent lens units is changed, wherein the second lens unit includes at least one positive lens and at least one negative lens, and wherein, when a refractive index of a material with respect to a wavelength of 400 nm is represented by Ns, a refractive index of the material with respect to a wavelength of 1,050 nm is represented by Nm, a refractive index of the material with respect to a wavelength of 1,700 nm is represented by Nl, and a relative partial dispersion θ of the material is expressed as:
θ=( Ns−Nm )/( Ns−Nl ),

the following conditional expression is satisfied:
−0.020<9 IR ( G 2 p ) AVE −θIR ( G 2 n ) AVE <0.015,

where θIR(G 2 p ) AVE represents an average value of relative partial dispersions of materials of the positive lens included in the second lens unit, and θIR(G 2 n ) AVE represents an average value of relative partial dispersions of materials of the negative lens included in the second lens unit.

2 . A zoom lens according to claim 1 , wherein, when an Abbe number ν of a material is expressed as:
ν=( Nm− 1)/( Ns−Nl ),

the following conditional expression is satisfied:
ν IR ( G 2 p ) AVE >18.0,

where νIR(G 2 p ) AVE represents an average value of Abbe numbers of materials of the positive lens included in the second lens unit.

3 . A zoom lens according to claim 1 , wherein the second lens unit includes a positive lens L 21 closest to the object side, and at least one surface of the positive lens L 21 has an aspherical shape.

4 . A zoom lens according to claim 1 , wherein the second lens unit includes, in order from the object side to the image side, a positive lens, and a cemented lens formed by cementing a negative lens and a positive lens.

5 . A zoom lens according to claim 1 , wherein the second lens unit includes, in order from the object side to the image side, a positive lens, a negative lens, a positive lens, a negative lens, and a positive lens.

6 . A zoom lens according to claim 1 , wherein the second lens unit includes a cemented lens formed by cementing a negative lens, a positive lens and a negative lens.

7 . A zoom lens according to claim 1 , wherein the second lens unit includes, in order from the object side to the image side, a positive lens, a positive lens, and a negative lens.

8 . A zoom lens according to claim 1 , wherein the second lens unit includes, in order from the object side to the image side, a positive lens, and a cemented lens formed by cementing a positive lens and a negative lens.

9 . A zoom lens according to claim 1 , wherein the first lens unit includes a negative lens that satisfies the following conditional expression:
ν IR ( G 1 n )>18.0,
where νIR(G 1 n ) represents an Abbe number of a material of the negative lens included in the first lens unit.

10 . A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.7<| F 1/ F 2|<1.0, where F 1 represents a focal length of the first lens unit, and F 2 represents a focal length of the second lens unit.

11 . A zoom lens according to claim 1 , wherein each of the at least one negative lens included in the second lens unit satisfies the following conditional expression:
θ IR ( G 2 n ) ALL <0.845,
where θIR(G 2 n ) ALL represents a relative partial dispersion of materials of each of the negative lens included in the second lens unit.

12 . A zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
ν IR ( G 2 n )>12.0,
θ IR ( G 2 n )<0.81,
where νIR(G 2 n ) and θIR(G 2 n ) represent an Abbe number and a relative partial dispersion of materials of at least one of the negative lens included in the second lens unit.

13 . A zoom lens according to claim 1 , further comprising a third lens unit having a positive refractive power on the image side of the second lens unit, the third lens unit being configured not to move during zooming.

14 . An image pickup apparatus, comprising:
a zoom lens comprising, in order from an object side to an image side:
a first lens unit having a negative refractive power;
an aperture stop; and
a second lens unit having a positive refractive power,
wherein the first lens unit and the second lens unit are configured to move during zooming so that an interval between each pair of adjacent lens units is changed,
wherein the second lens unit includes at least one positive lens and at least one negative lens, and
wherein, when a refractive index of a material with respect to a wavelength of 400 nm is represented by Ns, a refractive index of the material with respect to a wavelength of 1,050 nm is represented by Nm, a refractive index of the material with respect to a wavelength of 1,700 nm is represented by Nl, and a relative partial dispersion θ of the material is expressed as:
θ=( Ns−Nm )/( Ns−Nl ),

the following conditional expression is satisfied:
−0.020<θ IR ( G 2 p ) AVE −θIR ( G 2 n ) AVE <0.015,

where θIR(G 2 p ) AVE represents an average value of relative partial dispersions of materials of the positive lens included in the second lens unit, and θIR(G 2 n ) AVE represents an average value of relative partial dispersions of materials of the negative lens included in the second lens unit; and
an image pickup element configured to receive light of an image formed by the zoom lens.

Assignees

• Canon Kk

Inventors

• Nakano Masatsugu

Classifications

• G02B15/142

  having two groups only · CPC title

• G02B13/146

  with corrections for use in multiple wavelength bands, such as infrared and visible light, e.g. FLIR systems · CPC title

• G02B27/0025

  for optical correction, e.g. distorsion, aberration · CPC title

• G02B15/161

  Physics · mapped topic

• G02B15/177 Primary

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