Patent ID: 6239919
Filing Date: 2001-05-29
Classification: G02B

Abstract:
A large-relative-aperture internal focusing supertelephoto lens comprising, in order from the object side:a first lens group G1 possessing positive refractive power and comprising, in order from the object side, a front group G1F possessing positive refractive power and a rear group G1R possessing positive refractive power of the same order as the aforesaid front group G1F;a second lens group G2 possessing negative refractive power that carries out focusing as result of movement along an optical axis;and a third lens group G3 possessing positive refractive power;wherein the following conditional expressions are satisfied:0.7<.vertline.f1.multidot.f3/(f2.multidot.F).vertline.<1.3,0.4<.vertline.f2.multidot.F.vertline./(f1.multidot..PHI.1)<1.0,and0.7<f1F/f1R<1.4;where:f1=Focal length of the aforesaid first lens group G1,f2=Focal length of the aforesaid second lens group G2,f3=Focal length of the aforesaid third lens group G3,f1F=Focal length of the aforesaid front group within the first lens group G1,f1R=Focal length of the aforesaid rear group within the first lens group G1,F=Focal length of the entire lens system, and.PHI.1=Effective diameter of the lens surface at the object-most side of the aforesaid first lens group.