Zoom lens systems
AssigneePolaroid Corporation
InventorEllis I. Betensky
Life of this patent
Estimating the term…
Abstract
Zoom lens systems for use with moderately large image formats, such as those found in instant photography cameras, are provided. The systems include three lens units arranged in a negative/positive/negative power sequence and have a fixed aperture stop associated with the unit nearest the image. The positive unit is used for zooming and either the first or the third negative unit is used for compensating and focusing. Alternatively, the negative unit nearest the image is used for compensating and the negative unit farthest from the image is used for focusing. The systems achieve a long back focal length, a short front vertex to image distance, and in their simplest embodiments can consist of just three lens elements.
Claims22
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third lens unit which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- said first lens unit is moveable to focus the lens system and to compensate for changes in focus resulting from movement of said second lens unit;
- and
- said aperture stop is fixed during zooming of the lens system.
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third lens unit which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- said third lens unit is moveable to focus the lens system and to compensate for changes in focus resulting from movement of said second lens unit;
- and
- said aperture stop is fixed during zooming of the lens system.
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third lens unit which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said first lens unit is moveable to focus the lens system;
- said second lens unit is moveable to change the magnification of the lens system;
- said third lens unit is moveable to compensate for changes in focus resulting from movement of said second lens unit;
- and
- the aperture stop is fixed during zooming of the lens system.
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power whose absolute value is .vertline..PHI..sub.1 .vertline.;
- (b) a second lens unit which is on the image side of said first lens unit, said second lens unit having a positive optical power .PHI..sub.2 ;
- and
- (c) a third lens unit which is on the image side of said second lens unit, said third lens unit having a negative optical power whose absolute value is .vertline..PHI..sub.3 .vertline.;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- and
- the ratio of (.vertline..PHI..sub.1 .vertline.+.vertline..PHI..sub.3 .vertline.)/.PHI..sub.2 is between about 1.0 and about 1.5.
A zoom lens system for forming an image, said system having a maximum effective focal length f.sub.max and comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit, said second lens unit having a positive optical power and a focal length f.sub.2 ;
- and
- (c) a third lens unit which is on the image side of said second lens unit and has a negative optical power;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- and
- the ratio of f.sub.2 /f.sub.max is between about 0.10 and about 0.35.
A zoom lens system for forming an image, said system having a maximum effective focal length f.sub.max and a minimum effective focal length f.sub.min, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third lens unit which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- and
- the ratio of the magnification of tile aperture stop by said first and second lens units at f.sub.min to the magnification of the aperture stop by said first and second lens units at f.sub.max is less than about 2.0.
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third single lens unit consisting of a single lens element which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- said first lens unit is moveable to focus the lens system and to compensate for changes in focus resulting from movement of said second lens unit;
- and
- said aperture stop is fixed during zooming of the lens system.-Please
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third lens unit consisting of a single lens element which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said second lens unit is moveable to change the magnification of the lens system;
- said third lens unit is moveable to focus the lens system and to compensate for changes in focus resulting from movement of said second lens unit;
- and
- said aperture stop is fixed during zooming of the lens system.
A zoom lens system for forming an image, said system comprising:
- (a) a first lens unit having a negative optical power;
- (b) a second lens unit which is on the image side of said first lens unit and has a positive optical power;
- (c) a third lens unit consisting of a single lens element which is on the image side of said second lens unit and has a negative optical power;
- and
- (d) an aperture stop which is on the image side of said second lens unit;
- wherein:
- said first lens unit is moveable to focus the lens system;
- said second lens unit is moveable to change the magnification of the lens system;
- said third lens unit is moveable to compensate for changes in focus resulting from movement of said second lens unit;
- and
- the aperture stop is fixed during zooming of the lens system.
Dependencies are inferred from the claim text.