Zoom lens, and image pickup device using the same

A zoom lens system comprising, in order from an object side of said zoom lens system:

• a first lens group having a positive refracting power;
• a second lens group having negative refractive power;
• a third lens group having positive refracting power;
• and
• a fourth lens group having positive refracting power,
• wherein said third lens group comprises a negative lens element and a positive lens element, and said negative lens element is of meniscus shape concave on its image plane side, and
• any one negative lens in said second lens group satisfies the following condition:
• 0.59<(ng−nF)/(nF−nC) (8)
• where:
• nj (j is g, F and C) is a j-line refractive index of said negative lens.

A zoom lens system comprising, in order from an object side of said zoom lens 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 said first lens group comprises a negative lens element and a positive lens element, and said negative lens element is located on the object side of the positive lens element, and
• any one negative lens in said second lens group satisfies the following condition (8)
• 0.59<(ng−nF)/(nF−nC) (8)
• where:
• nj (j is g, F and C) is a j-line refractive index of said negative lens in said second lens group.

A zoom lens system comprising, in order from an object side of said zoom lens 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 said first lens group comprises a negative lens element and a positive lens element, and said negative lens element is of meniscus shape, and
• any one negative lens in said second lens group satisfies the following condition (8)
• 0.59<(ng−nF)/(nF−nC) (8)
• where:
• nj (j is g, F and C) is a j-line refractive index of said negative lens in said second lens group.

A zoom lens system comprising, in order from an object side of said zoom lens 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 said fourth lens group comprises a positive lens element and a negative lens element, and said negative lens element is located on the object side of said positive lens element, and
• any one negative lens in said second lens group satisfies the following condition (8)
• 0.59<(ng−nF)/(nF−nC) (8)
• where:
• nj (j is g, F and C) is a j-line refractive index of said negative lens in said second lens group.

A zoom lens system comprising, in order from an object side of said zoom lens 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 said fourth lens group comprises a negative lens element and a positive lens element, and said negative lens element is of meniscus shape concave on its object side, and
• any one negative lens in said second lens group satisfies the following condition (8)
• 0.59<(ng−nF)/(nF−nC) (8)
• where:
• nj (j is g, F and C) is a j-line refractive index of said negative lens in said second lens group.

A zoom lens system comprising, in order from an object side of said zoom lens system:

• a first lens group having a 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, and in which for zooming from wide angle-end to a telephoto end of said zoom system,
• an air separation between adjacent lens groups is varied,
• said third lens group is more toward the object side at said telephoto end than at said wide-angle end, wherein
• any one positive lens in said third lens group or said fourth lens group satisfies the following condition (9):
• 0.59<(ng−nF)/(nF−nC) (9)
• where:
• nj (j is g, F and C) is a j-line refractive index of said positive lens;
• a spacing between said first lens group and said second lens group is longer at said telephoto end than at said wide-angle end,
• a spacing between said second lens group and said third lens group is shorter at said telephoto end that at said wide-angle end, and
• a spacing between said third lens group and said fourth lens group is longer at said telephoto end than at said wide angle end.

A zoom lens system comprising, in order from an object side of said zoom lens 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 a lens located nearest to an object side of said fourth lens group is a negative lens element, and
• any one positive lens in said third lens group or said fourth lens group satisfies the following condition (9):
• 0.59<(ng−nF)/(nFnC) (9)
• where:
• nj (j is g, F and C) is a j-line refractive index of said positive lens;
• a spacing between said first lens group and said second lens group is longer at said telephoto end than at said wide-angle end,
• a spacing between said second lens group and said third lens group is shorter at said telephoto end than at said wide-angle end, and
• a spacing between said third lens group and said fourth lens group is longer at said telephoto end than at said wide-angle end.

A zoom lens system comprising, in order from an object side of said zoom lens 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 said third lens group comprises a negative lens element and a positive lens element, said negative lens element is of meniscus shape concave on its image plane side, said positive lens element is located on an object side of said negative lens element, and
• said positive lens element in said third lens group satisfies the following condition:
• 0.59<(ng−nF)/(nF−nC) (9)
• where:
• nj (j is g, F and C) is a j-line refractive index of said positive lens.