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US 2008/0304162 A1Published application
Zoom lens and image projection apparatus having the same
AssigneeCanon Kabushiki Kaisha
InventorShinji Yamasaki
Life of this patent
Estimating the term…
Abstract
A zoom lens includes a first lens unit having a negative optical power located closest to an enlargement side. In the zoom lens, a focal length of the zoom lens at a wide-angle end (fw) and a focal length of the first lens unit (f1) satisfy the following condition: −2.50<f1/fw<−1.36.
Claims9
A zoom lens including a first lens unit having a negative optical power located at a position closest to an enlargement side,
- wherein the focal length of the zoom lens at the wide-angle end (fw) and the focal length of the first lens unit (f1) satisfy the following condition:
- −2.50<f1/fw<−1.36.
A zoom lens comprising a first lens unit having a negative optical power located closest to an enlargement side,
- wherein the first lens unit includes one or more negative lenses having an aspheric surface, and
- wherein an effective diameter of a first aspheric surface that is the largest of the effective diameters of the aspheric surfaces of the one or more negative lenses (φmax), the focal length of the first aspheric surface (f1asp), a distance in a direction of an optical axis between a position of the first aspheric surface on the optical axis and a position of the first aspheric surface through which an outermost off-axis ray passes (Rdepth), the focal length of the zoom lens at a wide-angle end (fw), and the focal length of the first lens unit (f1) satisfy the following conditions:
- −2.50<f1/fw<−1.36
- −9.0<φmax/f1<−3.0
- −10.0<Rdepth/f1asp<−4.0.
2 more elements
Dependencies are inferred from the claim text.