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US 4,787,721 AGranted
Photographic lens system
AssigneeMinolta Camera Kabushiki Kaisha
InventorsAkira Fukushima, Yoshinobu Kudo
Life of this patent
Estimating the term…
Abstract
An improved compact telephoto type lens system is provided, including a front lens group of a positive refractive power having at least four lens components with one of the lens components having an aspheric surface and a rear lens group of a negative refractive power. The aspheric lens component can be a composite lens component of a glass substrate with a thin plastic aspheric surface.
Claims28
A photographic lens system comprising from the object side to the image side;
- a front lens unit of a positive refractive power including at least four lens components containing a front lens component with an aspheric surface;
- and
- a rear lens unit of a negative refractive power including a rear lens component with an aspheric surface;
- wherein the lens system fulfills the following condition when 0.5 R.sub.F <h<R.sub.F is maintained:
- ##EQU6## wherein, h;
- the height from the optical axis,
- t.sub.F (h);
- the thickness of the front lens component on the height h,
- r.sub.k ;
- the paraxial radius of curvature of the object side surface of the front lens component,
- r.sub.l ;
- the paraxial radius of curvature of the image side surface of the front lens component,
- d.sub.F ;
- the axial thickness of the front lens component, and
- R.sub.F ;
- the minimum value among .vertline.r.sub.k .vertline., .vertline.r.sub.l .vertline., and the effective height of the aspheric surface of the front lens component.
13 more elements
A photographic lens system comprising from the object side to the image side:
- a front lens unit of a positive refractive power including at least four lens components and having an aspheric surface, and
- a rear lens unit of a negative refractive power all of whose refractive surfaces are spheric, wherein the lens system fulfills the following condition when 0.5 R.sub.F <h<R.sub.F is maintained:
- ##EQU8## wherein, h;
- the height from the optical axis,
- t.sub.F (h);
- the thickness of the lens component having the aspheric surface in the front lens unit on the height h,
- r.sub.k ;
- the paraxial radius of curvature of the object side surface of the lens component having the aspheric surface in the front lens unit,
- r.sub.l ;
- the paraxial radius of curvature of the image side surface of the lens component having the aspheric surface in the front lens unit,
- d.sub.F ;
- the axial thickness of the lens component having the aspheric surface in the front lens unit, and
- R.sub.F ;
- the minimum value among .vertline.r.sub.k .vertline., .vertline.r.sub.l .vertline., and the effective height of the aspheric surface of the front lens unit.
11 more elements
Dependencies are inferred from the claim text.