Zoom lens and optical equipment using the same
AssigneeCanon Kabushiki Kaisha
InventorTakashi Shirasuna
Life of this patent
Estimating the term…
Abstract
A zoom lens includes a first lens unit having a positive optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a negative optical power in sequence from an object side. The zoom lens executes zooming by moving all the four lens units on an optical axis. At least one of the four lens units has at least one diffractive optical surface. By this arrangement, the size of the zoom lens can be easily reduced while securing a desired variable power ratio and correcting lateral chromatic aberration that is varied by zooming.
Claims34
A zoom lens, comprising in sequence from an object side:
- a first lens unit having a positive optical power;
- a second lens unit having a negative optical power;
- a third lens unit having a positive optical power;
- and
- a fourth lens unit having a negative optical power, wherein the zoom lens executes zooming by moving all said first, second, third, and fourth lens units along an optical axis, and at least one of said first, second, third, and fourth lens units has at least one diffractive optical surface.
Optical equipment, comprising:
- an optical-equipment element;
- and
- a zoom lens, connected to said optical-equipment element, said zoom lens comprising:
- a first lens unit having a positive optical power;
- a second lens unit having a negative optical power;
- a third lens unit having a positive optical power, and;
- a fourth lens unit having a negative optical power,
- wherein the zoom lens executes zooming by moving all of said first, second, third, and fourth lens units along an optical axis, and at least one of said first, second, third, and fourth lens units has at least one diffractive optical surface.
A method of magnifying light from an object with a zoom lens comprising:
- a first step of positively refracting light from the object with a first lens unit having a positive optical power;
- a second step of negatively refracting the light positively refracted by said first step with a second lens unit having a negative optical power;
- a third step of positively refracting the light negatively refracted by said second step with a third lens unit having a negative optical power;
- a fourth step of negatively refracting the light positively refracted by said third step with a fourth lens unit having a negative optical power;
- fifth step of forming an image of the object with light negatively refracted by said fourth step;
- a sixth step of changing the magnification of an image of the object formed in said fifth step by moving all of said first, second, third, and fourth lens units along an optical axis;
- and
- a seventh step of diffracting the light from the object with a diffractive optical surface on at least one of said first, second, third, and fourth lens units.
A device for correcting lateral chromatic aberrations in a zoom lens during zooming comprising:
- at least diffractive optical surface disposed on at least one of a first lens unit having positive optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a negative optical power disposed in sequence from an object to together constitute a zoom lens that executes zooming by moving all of the first, second, third, and fourth lens units along an optical axis, wherein the diffractive action of said at least one diffractive optical surface corrects lateral chromatic aberration of the zoom lens that occurs during zooming.
A method of correcting lateral chromatic aberration in a zoom lens having a first lens unit of positive optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a negative optical power, the zoom lens executing zooming by moving all of the first, second, third, and fourth lens units along an optical axis, said method comprising the steps of:
- diffracting light from an object that is:
- positively refracted with a first lens unit having a positive refractive power with at least one diffractive optical surface on the first lens unit;
- positively refracted with a first lens unit having a positive refractive power and then negatively refracted by a second lens unit having a negative optical power with at least one diffractive optical surface on the second lens unit;
- positively refracted with a first lens unit having a positive refractive power and then negatively refracted by a second lens unit having a negative refractive power and then positively refracted by a third lens unit having a positive refractive power with at least one diffractive optical surface on the third lens unit;
- or
- positively refracted with a first lens unit having a positive refractive power, then negatively refracted by a second lens unit having a negative refractive power, then positively refracted by a third lens unit having a positive refractive power, and then negatively refracted by a fourth lens unit having a negative refractive power with at least one diffractive optical surface on the fourth lens unit.
Dependencies are inferred from the claim text.