Variable power view finder
AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorsTakayuki Ito, Sachio Hasushita
Life of this patent
Estimating the term…
Abstract
A real image type of variable power view finder is disclosed which has an objective lens system, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed. The objective lens system includes negative and positive lens groups located in this order from the object side, so as to vary the distance therebetween, to change the magnification. The negative lens group of the objective lens system has at least two negative lenses.
Claims36
A real image type variable power view finder having an objective lens system, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, wherein;
- said objective lens system comprises a first lens group having negative power and a second lens group having positive power located in this order from an object side;
- a distance between said first and said second lens groups is varied to change magnification;
- and wherein,
- said first lens group of said objective lens system comprises at least two negative lens elements, wherein one of said at least two negative lens elements, closest to the object to be photographed comprises two aspheric lens surfaces.
A real image type variable power view finder having an objective lens system, and image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, said objective lens system comprising a first lens group having negative power, a second lens group having negative power, and a third lens group having positive power, located in this order from an object side, so that said first lens group is stationary and said second lens group and said third lens group are movable toward and away from said first lens group to vary magnification.
A real image type view finder having an objective lens system, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, wherein;
- said eyepiece lens system comprises a first lens group having positive power and a second lens group having negative power, located in this order from an object side;
- and,
- said second lens group comprises a negative lens element having a concave surface on a viewer's eye side and satisfying the following relationships:
- -0.48.ltoreq.fE/fEN<0,
- and
- 0.5<fE/rE<3.5,
- wherein fE designates a focal length of said eyepiece lens system, fEN designates a focal length of said negative lens element of said eyepiece lens system, and rE designates a radius of curvature of a concave surface of said eyepiece lens system closest to a viewer's eye.
A real image type view finder having an objective lens system, a condenser lens, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, wherein;
- said eyepiece lens system comprises a positive lens group and a negative lens group, located in this order from an object side;
- and wherein,
- said condenser lens, said image erecting optical system and said eyepiece lens system satisfy the following relationships;
- 0.15<LE/fE<0.5
- 0.9<fBE/fE<1.3
- wherein fE designates a focal length of said eyepiece lens system, LE designates a distance between said condenser lens and said image erecting optical system, and fBE designates a conversion value in terms of distance between said condenser lens and said eyepiece lens system.
An optical system comprising a first lens element having two aspheric lens surfaces with a negative power, and a second lens element having at least one aspheric lens surface with a positive power, said first and said second lens elements satisfying the following relationships:
- .vertline.SF1.vertline.<1
- 0.ltoreq..vertline..vertline.SF1.vertline.-.vertline.SF2.vertline..vertline ..ltoreq.4
- wherein SF1 designates a shape factor of said first lens element, and SF2 a shape factor of said second lens element, and wherein the shape factor SF is defined by SF=(r1+r2)/(r2-r1), r1 and r2 designating respective radii of curvature of opposite lens surfaces of a designated lens element.
An image forming optical system comprising;
- a first lens group having negative power;
- a second lens group having positive power;
- wherein magnification is varied in accordance with a distance between said first and said second lens groups;
- wherein said first lens group comprises a first lens element having two aspheric lens surfaces and a second lens element having at least one aspheric lens surface, and said first and said second lens elements satisfy the following relationships;
- .vertline.SF1.vertline.<1
- 0.ltoreq..vertline..vertline.SF1.vertline.-.vertline.SF2.vertline..vertline ..ltoreq.4
- wherein SF1 designates a shape factor of said first lens element of said first lens group, and SF2 designates a shape factor of said second lens element of said first lens group, and wherein the shape factor SF is defined by SF=(r1+r2)/(r2-r1), r1 and r2 designating respective radii of curvature of opposite lens surfaces of a lens element.
A real image type variable power view finder having an objective lens system, and image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, wherein;
- said objective lens system comprises a first lens group having negative power and a second lens group having positive power located in this order from an object side;
- a distance between said first and said second lens groups is varied to change magnification;
- and
- wherein said first lens group comprises a first negative lens element, a second negative lens element, and a third positive lens element, located in this order from the object side.
A real image type variable power view finder having an objective lens system, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, wherein;
- said objective lens system comprises a first lens group having negative power and a second lens group having positive power located in this order from an object side;
- a distance between said first and said second lens groups is varied to change magnification;
- wherein said first lens group of said objective lens system comprises at least two negative lens elements;
- and
- wherein said second lens group of said objective lens system comprises a positive lens element and a negative lens element, located in this order from the object side.
A real image type variable power view finder having an objective lens system, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, wherein;
- said objective lens system comprises a first lens group having negative power and a second lens group having positive power located in this order from an object side;
- a distance between said first and said second lens groups is varied to change magnification;
- and,
- wherein said first lens group of said objective lens system comprises a first lens element having negative power and a second lens element having negative power, both surfaces of said first lens element are aspherical, and at leans one surface of said second lens element is aspherical.
A real image type view finder having an objective lens system, an image erecting optical system, and an eyepiece lens system, located in this order as viewed from an object to be photographed, said eyepiece lens system consisting of a first lens having a positive power and a second lens having a negative power, located in this order from an object side, said second lens having a concave surface on a viewer's eye side and satisfying the following relationships:
- -0.7<fE/fEN<0,
- 0.5<fE/rE<3.5,
- wherein fE designates a focal length of said eyepiece lens system, fEN designates a focal length of said second lens, and rE designates a radius of curvature of a concave surface of said eyepiece lens system closest to a viewer's eye.
Dependencies are inferred from the claim text.