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US 4,892,397 AGranted
Photographic lens having ghost image prevented from appearing
AssigneeCanon Kabushiki Kaisha
InventorAkihisa Horiuchi
Life of this patent
Estimating the term…
Abstract
In the photographic optical system comprised of a plurality of lenses and having a filter in between the lenses, a light beam emerging from a lens on the object side of the filter is arranged to diverge to prevent the light reflected from a solid state image pickup element on a predetermined image plane from being reflected again by the filter to re-focus on the predetermined image plane.
Claims7
A zoom lens comprising:
- from front to rear,
- a first lens unit having a positive refractive power;
- a second lens unit for variation of the image magnification having a negative refractive power;
- a third lens unit for compensating for the shift of an image plane resulting from the variation of the image magnification;
- a fourth lens unit;
- a fifth lens unit having a positive refractive power and hving an image forming function,
- wherein the following condition is satisfied:
- 1.05<f.sub.4 /L<1.3
- where L is the absolute value of a distance from a point of convergence of an on-axial light beam which has passed said first lens unit through said third lens unit to a front principal point of said fourth lens unit, and f.sub.4 is a focal length of said fourth lens unit.
6 more elements
Dependencies are inferred from the claim text.