Zoom lens device with inner focusing method
AssigneeCanon Kabushiki Kaisha
InventorFumiaki Usui
Life of this patent
Estimating the term…
Abstract
A zoom lens device including in order of lens units from the lens unit closest to an object side of the zoom lens device to an image side of the zoom lens device, a first lens unit having a positive refractive power, a second lens unit for changing magnification and having a negative refractive power, a third lens unit for correcting changes in an image plane which occur as the magnification changes, and a fourth lens unit for forming an image. The first lens unit includes (i) a front lens subunit which is stationary during focusing and which has a positive refractive power and (ii) a rear lens subunit which is movable in order to bring an object into focus. The front lens subunit includes a negative lens and a positive lens. The rear lens subunit includes a negative lens and at least two positive lenses.
Claims20
A zoom lens comprising in order from object side to image side of said zoom lens:
- a first lens unit having a positive refractive power;
- a second lens unit for changing magnification and having a negative refractive power;
- a third lens unit for correcting changes in an image plane which occur as the magnification changes;
- and
- a fourth lens unit for forming an image,
- wherein said first lens unit comprises (i) a front lens subunit which is stationary during focusing and (ii) a rear lens subunit which is movable for focusing,
- said front lens subunit comprising a negative lens and a positive lens, and
- said rear lens subunit comprising a negative lens, being the closest or second closest of all lenses of said rear lens subunit to the object side of said rear lens subunit, and at least two positive lenses positioned on the image side of said negative lens.
Dependencies are inferred from the claim text.