Patent ID: 6353505
Filing Date: 2002-03-05
Classification: G02B

Abstract:
A zoom lens system comprising a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group, in this order from an object;wherein upon zooming from the short focal length extremity to the long focal length extremity, said first through fourth lens groups move toward said object so that the distance between said first and said second lens groups becomes longer, the distance between said second and said third lens groups becomes shorter, and the distance between said third and said fourth lens groups becomes shorter; wherein said third lens group comprises a positive 3-1st lens element, a positive 3-2nd lens element having a large-curvature convex surface facing toward said object, and a negative 3-3rd lens element having a large-curvature concave surface facing toward said object, in this order from said object; and wherein said zoom lens system satisfies the following condition: âˆ’1.83-3-1/Ã˜wwhereinÃ˜r3-3-1 designates the surface power of the object-side surface of said negative 3-3rd lens element of said third lens group; and Ã˜w designates the power of the entire lens system at the short focal length extremity.