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US 12,164,089 B2Granted
Extender lens unit, zoom lens, and image pickup apparatus
AssigneeCanon Kabushiki Kaisha
InventorYosuke Eguchi
Life of this patent
Estimating the term…
Abstract
An extender lens unit to be inserted into and removed from an optical path in a relay lens unit included in a zoom lens consists of a front unit having a positive refractive power, a middle unit having a negative refractive power, and a rear unit having a negative refractive power. The extender lens unit includes three negative lenses. The middle unit includes a negative lens. An average refractive index of positive lenses included in the extender lens unit, an average refractive index of negative lenses included in the extender lens unit, a focal length of the negative lens included in the middle unit, and a focal length of the middle unit are appropriately set.
Claims11
An extender lens unit insertable into and removable from an optical path in a relay lens unit included in a zoom lens, the extender lens unit consisting of:
- a front unit having a positive refractive power;
- a middle unit having a negative refractive power;
- and
- a rear unit having a negative refractive power,
- wherein the front unit, the middle unit, and the rear unit comprise seven or more lenses,
- wherein the front unit, the middle unit, and the rear unit include positive lenses and three negative lenses among the seven or more lenses,
- wherein the middle unit includes one negative lens, among the three negative lenses,
- wherein the front unit includes one of the positive lenses arranged closest to an object side, and
- wherein the following conditional expressions are satisfied:
- 0.20<Nn−Np<0.60;
- and
- 0.20<fbna/fb<1.00,
- 2.38≤fb/fc<8.00;
- and
- 10.0<vdp−vdn<40.0,
- where Np and Nn represent an average refractive index of the positive lenses and an average refractive index of the three negative lenses, respectively, fbna represents a focal length of the one negative lens included in the middle unit, fb represents a focal length of the middle unit, fc represents a focal length of the rear unit, and vdp and vdn represent an average Abbe number of the positive lenses and an average Abbe number of the three negative lenses, respectively.
13 more elements
A zoom lens comprising in order from an object side to an image side:
- a zoom lens unit configured to move along an optical axis during zooming;
- and
- a relay lens unit configured not to move along the optical axis during zooming,
- wherein the relay lens unit includes an extender lens unit, which is insertable into and removable from an optical path in the relay lens unit,
- wherein the extender lens unit consists of:
- a front unit having a positive refractive power;
- a middle unit having a negative refractive power;
- and
- a rear unit having a negative refractive power,
- wherein the front unit, the middle unit, and the rear unit comprise seven or more lenses,
- wherein the front unit, the middle unit, and the rear unit include positive lenses and three negative lenses among the seven or more lenses,
- wherein the middle unit includes one negative lens, among the three negative lenses,
- wherein the front unit includes one of the positive lenses arranged closest to an object side, and
- wherein the following conditional expressions are satisfied:
- 0.20<Nn−Np<0.60;
- and
- 0.20<fbna/fb<1.00,
- 2.38≤fb/fc<8.00;
- and
- 10.0<vdp−vdn<40.0,
- where Np and Nn represent an average refractive index of the positive lenses and an average refractive index of the three negative lenses, respectively, fbna represents a focal length of the one negative lens included in the middle unit, fb represents a focal length of the middle unit, fc represents a focal length of the rear unit, and vdp and vdn represent an average Abbe number of the positive lenses and an average Abbe number of the three negative lenses, respectively.
18 more elements
An image pickup apparatus comprising:
- a zoom lens;
- and
- an image pickup element configured to receive light of an image formed by the zoom lens,
- wherein the zoom lens comprises, in order from an object side to an image side:
- a zoom lens unit configured to move along an optical axis during zooming;
- and
- a relay lens unit configured not to move along the optical axis during zooming,
- wherein the relay lens unit includes an extender lens unit, which is insertable into and removable from an optical path in the relay lens unit,
- wherein the extender lens unit consists of:
- a front unit having a positive refractive power;
- a middle unit having a negative refractive power;
- and
- a rear unit having a negative refractive power,
- wherein the front unit, the middle unit, and the rear unit comprise seven or more lenses,
- wherein the front unit, the middle unit, and the rear unit include positive lenses and three negative lenses among the seven or more lenses,
- wherein the middle unit includes one negative lens, among the three negative lenses,
- wherein the front unit includes one of the positive lenses arranged closest to an object side, and
- wherein the following conditional expressions are satisfied:
- 0.20<Nn−Np<0.60;
- and
- 0.20<fbna/fb<1.00,
- 2.38≤fb/fc<8.00;
- and
- 10.0<vdp−vdn<40.0,
- where Np and Nn represent an average refractive index of the positive lenses and an average refractive index of the three negative lenses, respectively, fbna represents a focal length of the one negative lens included in the middle unit, fb represents a focal length of the middle unit, fc represents a focal length of the rear unit, and vdp and vdn represent an average Abbe number of the positive lenses and an average Abbe number of the three negative lenses, respectively.
22 more elements
Dependencies are inferred from the claim text.