US 8,477,429 B2Granted

Zoom lens system and image pickup apparatus including the same

AssigneeCanon Kabushiki Kaisha

InventorsMasao Hori, Youtarou Sanjou

Life of this patent

Estimating the term…

Loading patent…

Abstract

A zoom lens system includes, in order from object-side to image-side a positive first lens unit, a second negative lens unit, a third lens unit, and a fourth positive lens unit. The fourth unit includes a front subunit having positive power and a rear subunit having positive power. The following conditions are satisfied: −2.100×10−3×νd+0.693<θgF; 0.555<θgF<0.900; 0.8<(νfp/νfn)/(νrp/νrn)<4.0; 0.8<|{(θfn−θfp)/(νfp−νfn)}/{(θrn−θrp)/(νrp−νrn)}|, where vd and θgF indicate Abbe number and partial dispersion ratio of a lens included in the rear subunit, respectively, and where νfp, θfp, νfn and θfn indicate averages of Abbe number and partial dispersion ratio of positive lenses and averages of Abbe number and partial dispersion ratio of negative lenses included in the front subunit, respectively; νrp, θrp, νrn and θrn indicate averages of Abbe number and partial dispersion ratio of positive lenses and averages of Abbe number and partial dispersion ratio of negative lenses included in the rear subunit, respectively.

Claims15

Dependent claims

A zoom lens system comprising, in order from an object side to an image side:

a first lens unit which does not move for zooming and has a positive refractive power;
a second lens unit which moves to the image side during zooming from a wide angle end to a telephoto end and has a negative refractive power;
a third lens unit which moves on an optical axis during zooming;
and
a fourth lens unit which does not move during zooming and has a positive refractive power,
wherein the fourth lens unit is constituted by a front lens subunit having a positive refractive power and a rear lens subunit having a positive refractive power with an air interval therebetween, which air interval being the largest within the fourth lens unit,
wherein the front lens subunit and the rear lens subunit each have at least one positive lens and at least one negative lens,
wherein the fourth lens unit satisfies the following conditions:
0.8<(νfp/νfn)/(νrp/νrn)<4.0;
and
0.8<|{(θfn−θfp)/(νfp−νfn)}/{(θrn−θrp)/(νrp−νrn)}|,
where νfp and θfp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of positive lenses included in the front lens subunit, respectively, νfn and θfn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the front lens subunit, respectively, νrp and θrp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the positive lenses included in the rear lens subunit, respectively, νrn and θrn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the rear lens subunit, respectively, wherein the following condition is satisfied:
1.8<fGNL/f42<6.5,
where fGNL represents a focal length of the lens GNL and f42 represents a focal length of the rear lens subunit,
wherein the rear lens subunit includes a lens GNL formed of a material having a characteristic satisfying:
−2.100×10−3×νd+0.693<θgF;
and
0.555<θgF<0.900,
where νd indicates an Abbe number of the material and θgF indicates a partial dispersion ratio, with respect to a g-line and an F-line, of the material, and
wherein the Abbe number νd and the partial dispersion ratio θgF with respect to the g-line and the F-line satisfying:
νd=(Nd−1)/(NF−NC);
and
θgF=(Ng−NF)/(NF−NC),
where Ng, NF, Nd, and NC denote refractive indexes with respect to the g-line at 435.8 nm, the F-line 486.1 nm, a d-line 587.8 nm and a C-line 656.3 nm of the material, respectively.

21 more elements

An image pickup apparatus comprising:

an image pickup element for receiving an image of a subject;
and
a zoom lens system for forming the image of the subject on the image pickup element,
wherein the zoom lens system includes, in order from a subject side to an image side:
a first lens unit which does not move for zooming and has a positive refractive power;
a second lens unit which moves to the image side during zooming from a wide angle end to a telephoto end and has a negative refractive power;
a third lens unit which moves on an optical axis in conjunction with the movement of the second lens unit and has a negative refractive power;
and
a fourth lens unit which does not move during zooming and has a positive refractive power,
wherein the fourth lens unit is constituted by a front lens subunit having a positive refractive power and a rear lens subunit having a positive refractive power with an air interval therebetween, which air interval being the largest within the fourth lens unit,
wherein the front lens subunit and the rear lens subunit each have at least one positive lens and at least one negative lens,
wherein the fourth lens unit satisfies the following conditions:
0.8<(νfp/νfn)/(νrp/νrn)<4.0;
and
0.8<|{(θfn−θfp)/(νfp−νfn)}/{(θrn−θrp)/(νrp−νrn)}|,
where νfp and θfp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the positive lenses included in the front lens subunit, respectively, νfn and θfn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the front lens subunit, respectively, νrp and θrp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the positive lenses included in the rear lens subunit, respectively, νrn and θrn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the rear lens subunit, respectively,
wherein the following condition is satisfied:
1.8<fGNL/f42<6.5,
where fGNL represents a focal length of the lens GNL and f42 represents a focal length of the rear lens subunit,
wherein the rear lens subunit includes a lens GNL formed of a material having a characteristic satisfying:
−2.100×10−3×νd+0.693<θgF;
and
0.555<θgF<0.900,
where νd indicates an Abbe number of the material and θgF indicates a partial dispersion ratio, with respect to a g-line and an F-line, of the material, and
wherein the Abbe number νd and the partial dispersion ratio θgF with respect to the g-line and the F-line satisfying:
νd=(Nd−1)/(NF−NC);
and
θgF=(Ng−NF)/(NF−NC),
where Ng, NF, Nd, and NC denote refractive indexes with respect to the g-line at 435.8 nm, the F-line at 486.1 nm, a d-line at 587.8 nm and a C-line at 656.3 nm of the material, respectively.

26 more elements

An image pickup apparatus comprising:

an image pickup element for receiving an image of a subject;
and
a zoom lens system for forming the image of the subject on the image pickup element,
wherein the zoom lens system includes, in order from a subject side to an image side:
a first lens unit which does not move for zooming and has a positive refractive power;
a second lens unit which moves to the image side during zooming from a wide angle end to a telephoto end and has a negative refractive power;
a third lens unit which moves on an optical axis in conjunction with the movement of the second lens unit and has a negative refractive power;
and
a fourth lens unit which does not move during zooming and has a positive refractive power,
wherein the fourth lens unit is constituted by a front lens subunit having a positive refractive power and a rear lens subunit having a positive refractive power with an air interval therebetween, which air interval being the largest within the fourth lens unit,
wherein the front lens subunit and the rear lens subunit each have at least one positive lens and at least one negative lens,
wherein the fourth lens unit satisfies the following conditions:
0.8<(νfp/νfn)/(νrp/νrn)<4.0;
and
0.8<|{(θfn−θfp)/(νfp−νfn)}/{(θrn−θrp)/(νrp−νrn)}|,
where νfp and θfp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the positive lenses included in the front lens subunit, respectively, νfn and θfn indicate an average value of Abbe number and an average value of partial dispersion ratios θqF of materials of the negative lenses included in the front lens subunit, respectively, νrp and θrp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the positive lenses included in the rear lens subunit, respectively, νrn and θrn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the rear lens subunit, respectively,
wherein the rear lens subunit includes a lens GNL formed of a material having a characteristic satisfying:
−2.100×10−3×νd+0.693<θgF;
and
0.555<θgF<0.900,
where νd indicates an Abbe number of the material and θgF indicates a partial dispersion ratio, with respect to a g-line and an F-line, of the material, and
wherein the Abbe number νd and the partial dispersion ratio θgF with respect to the g-line and the F-line satisfying:
νd=(Nd−1)/(NF−NC);
and
θgF=(Ng−NF)/(NF−NC),
where Ng, NF, Nd, and NC denote refractive indexes with respect to the g-line at 435.8 nm, the F-line at 486.1 nm, a d-line at 587.8 nm and a C-line at 656.3 nm—;
of the material, respectively,
wherein the fourth lens unit further comprises a magnification-varying optical system which is removably insertable;
onto an optical path between the front lens subunit and the rear lens subunit, and
wherein the following condition is satisfied:
0.7<h—k/h—k—1<2.5,
where h_k indicates a beam diameter of an on-axial beam incident on a first lens surface of the magnification-varying optical system and h_k—1 indicates a beam diameter of an on-axial beam emerged from a final lens surface of the magnification-varying optical system.

29 more elements

A zoom lens system comprising, in order from an object side to an image side:

a first lens unit which does not move for zooming and has a positive refractive power;
a second lens unit which moves to the image side during zooming from a wide angle end to a telephoto end and has a negative refractive power;
a third lens unit which moves on an optical axis during zooming;
and
a fourth lens unit which does not move during zooming and has a positive refractive power,
wherein the fourth lens unit is constituted by a front lens subunit having a positive refractive power and a rear lens subunit having a positive refractive power with an air interval therebetween, which air interval being the largest within the fourth lens unit,
wherein the front lens subunit and the rear lens subunit each have at least one positive lens and at least one negative lens,
wherein the fourth lens unit satisfies the following conditions:
0.8<(νfp/νfn)/(νrp/νrn)<4.0;
and
0.8<|{(θfn−θfp)/(νfp−νfn)}/{(θrn−θrp)/(νrp−νrn)}|,
where νfp and θfp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of positive lenses included in the front lens subunit, respectively, νfn and θfn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the front lens subunit, respectively, νrp and θrp indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the positive lenses included in the rear lens subunit, respectively, νrn and θrn indicate an average value of Abbe number and an average value of partial dispersion ratios θgF of materials of the negative lenses included in the rear lens subunit, respectively,
wherein the rear lens subunit includes a lens GNL formed of a material having a characteristic satisfying:
−2.100×10−3×νd+0.693<θgF;
and
0.555<θgF<0.900,
where νd indicates an Abbe number of the material and θgF indicates a partial dispersion ratio, with respect to a g-line and an F-line, of the material, and
wherein the Abbe number νd and the partial dispersion ratio θgF with respect to the g-line and the F-line satisfying:
νd=(Nd−1)/(NF−NC);
and
θgF=(Ng−NF)/(NF−NC),
where Ng, NF, Nd, and NC denote refractive indexes with respect to the g-line at 435.8 nm, the F-line at 486.1 nm, a d-line at 587.8 nm and a C-line at 656.3 nm of the material, respectively,
wherein the fourth lens unit further comprises a magnification-varying optical system which is removably insertable onto an optical path between the front lens subunit and the rear lens subunit, and
wherein the following condition is satisfied:
0.7<h—k/h—k—1<2.5,
where h_k indicates a beam diameter of an on-axial beam incident on a first lens surface of the magnification-varying optical system and h_k—1 indicates a beam diameter of an on-axial beam emerged from a final lens surface of the magnification-varying optical system.

23 more elements

Dependencies are inferred from the claim text.