Compact zoom lens
AssigneeEastman Kodak Company
InventorsWilliam T. Goosey, Kazunaga Shimizu
Life of this patent
Estimating the term…
Abstract
A zoom lens comprises a plurality of lens elements arranged into three zooming lens units. These zooming lens units are spaced from one another by axial distances that vary during zooming. The lens units are a negative power front lens unit, a positive power middle lens unit and a negative power rear lens unit. At least one of the lens units continually moves away from the image plane, as the zoom lens zooms from a wide angle position toward a telephoto position so that the distance from this lens unit to the image plane varies in sigmoidal relation with respect to the focal length of the zoom lens.
Claims19
A zoom lens having a focal length that changes from one zoom position to another zoom position, said zoom lens creating an image at an image plane and comprising:
- a plurality of lens elements arranged in three zooming lens units spaced from one another by axial distances that vary during zooming, wherein at least one of said three lens units continually moves away from said image plane as said zoom lens zooms from a wide angle position toward a telephoto position, so that the distance from said one lens unit to said image plane varies in a sigmoidal relation with respect to said focal length of said zoom lens, said three lens units being
- (i) a negative power front lens unit;
- (ii) a positive power middle lens unit, accepting light from said negative power front lens unit;
- and
- (iii) a negative power rear lens unit, accepting light from said positive power middle lens unit.
A zoom lens having a focal length that changes from one zoom position to another zoom position, said zoom lens creating an image on an image plane and comprising a plurality of lens elements arranged in three zooming lens units spaced from one another by axial distances that vary during zooming, said zoom lens being characterized by
- (i) a negative power front lens unit;
- (ii) a positive power middle lens unit, accepting light from said negative power front lens unit;
- (iii) a negative power rear lens unit, accepting light from said positive power middle lens unit;
- and
- (iv) one of said lens units continually moving away from said image plane as said zoom lens zooms from a wide angle position toward a telephoto position (1) at a first rate as said zoom lens moves from said wide angle position to a first intermediate position, (2) at a second, slower rate as said zoom lens moves from said first intermediate position to a second intermediate position, and (3) at a third rate which is faster than said second rate, when said zoom lens moves from said second intermediate position toward said telephoto position.
A zoom lens having a focal length that changes from one zoom position to another zoom position, said zoom lens creating an image on an image plane and comprising a plurality of lens elements arranged in three zooming lens units spaced from one another by axial distances that vary during zooming, said zoom lens being characterized by
- (i) a negative power front lens unit spaced from the image plane by a predetermined distance, said predetermined distance continually increasing as said zoom lens zooms from a wide angle position toward a telephoto position, and said front lens unit moves away from said image plane (1) at a first rate as said zoom lens moves from said wide angle position to a first intermediate position, (2) at a second, slower rate as said zoom lens moves from said first intermediate position to a second intermediate position, and (3) at a third rate which is faster than said second rate, when said zoom lens moves from said second intermediate position towards said telephoto position;
- (ii) a positive power middle lens unit, accepting light from said negative power front lens unit;
- and
- (iii) a negative power rear lens unit, accepting light from said positive power middle lens unit;
- and wherein said zoom lens satisfies the following inequalities;
- ##EQU3## where Ft is the focal length of said zoom lens in said telephoto position,
- Fw is the focal length of said zoom lens in said wide angle position,
- FVFPt is a front vertex to image plane distance when said zoom lens is in said telephoto position, and
- FVFPo is a front vertex to image plane distance when the zoom lens is in any zoom position other than said telephoto position.
A zoom lens providing an image at an image plane and having a focal length that changes from one zoom position to another zoom position, said zoom lens comprising a plurality of lens elements arranged in three zooming lens units spaced from one another by axial distances that vary during zooming, said zoom lens being characterized by
- a negative power front lens unit;
- a positive power middle lens unit, accepting light from said negative power front lens unit;
- and
- a negative power rear lens unit, accepting light from said positive power middle lens unit;
- and
- wherein (1) each one of said lens units is continually movable away from the image plane as said zoom lens zooms from a wide angle position to a telephoto position, (2) one of said lens units is being positioned a predetermined distance away from another one of said lens units, said predetermined distance continuously (A) increases as said zoom lens zooms from said wide angle position to an intermediate position, and (B) continuously decreases as said zoom lens zooms from said intermediate position to said telephoto position;
- and (3) said zoom lens satisfies the following inequalities;
- ##EQU4## where Ft is the focal length of said zoom lens in said telephoto position,
- Fw is the focal length of said zoom lens in said wide angle position,
- FVFPt is a front vertex to image plane distance when said zoom lens is in said telephoto position, and
- FVFPo is a front vertex to image plane distance when the zoom lens is in any zoom position other than said telephoto position.
Dependencies are inferred from the claim text.