Zoom lens system

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, and satisfying the following condition (1):

• 0.5<|F2/F3|<1.2 (1)
• where Fi is a focal length of an i-th lens group.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, and satisfying the following condition (2):

• 0.49<|L3/L2|<1 (2)
• where Li is an amount of movement of an i-th lens group from the wide-angle end to the telephoto end.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, and satisfying the following condition (3):

• 2<(F3.4W)/IH<3.3 (3)
• where (F3.4W) is a composite focal length of said third and fourth lens groups at the wide-angle end, and IH is a radius of an image circle.

A zoom lens system comprising, in order from an object side of said system, a first lens group having positive refracting power, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group having positive refracting power and a fourth lens group that has positive refracting power and is movable during zooming, wherein:

• said third lens group comprises, in order from an object side thereof, a positive lens convex on an object side thereof and a doublet consisting of a positive lens convex on an object side thereof and a negative lens concave on an image side thereof, and peripheries of object side-directed convex surfaces of both said object-side positive lens and said doublet in said third lens group are held by a lens holder barrel while said convex surfaces are abutting at said peripheries or some points on said lens holder barrel.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, and satisfying the following conditions (1) and (2):

• 0.5<|F2/F3|<1.2 (1)
• 0.49<|L3/L2|<1 (2)
• where Fi is a focal length of an i-th lens group, and Li is an amount of movement of an i-th lens group from the wide-angle end to the telephoto end.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, and satisfying the following conditions (1) and (3):

• 0.5<|F2/F3|<1.2 (1)
• 2<(F3.4W)/IH<3.3 (3)
• where Fi is a focal length of an i-th lens group, (F3.4W) is a composite focal length of said third and fourth lens groups at the wide-angle end, and IH is a radius of an image circle.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, and satisfying the following conditions (2) and (3):

• 0.49<|L3/L2|<1 (2)
• 2<(F3.4W)/IH<3.3 (3)
• where Li is an amount of movement of an i-th lens group from the wide-angle end to the telephoto end, (F3.4W) is a composite focal length of said third and fourth lens groups at the wide-angle end, and IH is a radius of an image circle.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, wherein said first lens group consists of one positive lens, and a lens in said second lens group that is located nearest to an object side thereof is a negative lens that satisfies the following condition (7):

• ν21<40 (7)
• where ν21 is an Abbe's number of said negative lens located nearest to the object side of said second lens group.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves constantly from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, wherein said third lens group comprises a doublet consisting of a positive lens and a negative lens, and said fourth lens group consists of one positive lens.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves constantly from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, wherein each of said second and third lens groups comprises a doublet consisting of a positive lens and a negative lens.

A zoom lens system comprising, in order from an object side of said system, a first lens group that has positive refracting power and remains fixed during zooming, a second lens group that has negative refracting power and moves from an object side to an image plane side of said system during zooming from a wide-angle end to a telephoto end of said system, a third lens group that has positive refracting power and moves constantly from the image plane side to the object side during zooming from the wide-angle end to the telephoto end and a fourth lens group that has positive refracting power and is movable during zooming, wherein said third lens group consists of, in order from an object side thereof, a positive lens, and a doublet consisting of a positive lens and a negative lens.

A zoom lens system comprising, in order from an object side of said system, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power and a fourth lens group having positive refracting power, wherein during zooming, a space between said first and second lens groups, a space between said second and third lens groups and a space between said third and fourth lens groups vary independently, said third lens group consists of, in order from an object side thereof, a double-convex positive lens, and a doublet consisting of a positive meniscus lens convex on an object side thereof and a negative meniscus lens, and said fourth lens group consists of a double-convex lens having a large curvature on an object side surface thereof.

A zoom lens system comprising, in order from an object side of said system, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power and a fourth lens group having positive refracting power, wherein during zooming, a space between said first and second lens groups, a space between said second and third lens groups and a space between said third and fourth lens groups vary independently, said first lens group consists of one positive lens, said second lens group comprises three lenses or, in order from an object side thereof, a single lens and a doublet consisting of a negative lens and a positive lens, said third lens group comprises three lenses or, in order from an object side thereof, a single lens and a doublet consisting of a positive lens and a negative lens, and said fourth lens group consists of one positive lens.

A zoom lens system comprising, in order from an object side of said system, a first lens group having positive refracting power, a second lens group having negative refracting power, a third lens group having positive refracting power and a fourth lens group having positive refracting power, wherein during zooming, a space between said first and second lens groups, a space between said second and third lens groups and a space between said third and fourth lens groups vary independently, said first lens group consists of two lenses or a positive lens and a negative lens, and said second or third lens group comprises a doublet consisting of at least one set of a positive lens and a negative lens.