Patent ID: 6931207
Filing Date: 2005-08-16
Classification: G02B

Abstract:
1. A zoom lens system comprising in order from an object side to an image side: a first lens unit with a positive optical power, the first lens unit having at least one positive lens element and at least one negative lens element; a second lens unit with a negative optical power; a third lens unit with a positive optical power, the third lens unit consisting of a first lens sub-unit with a positive optical power and a second lens sub-unit with a positive optical power disposed with the largest spacing between them, the first lens sub-unit having at least two positive lens elements; and a fourth lens unit with a positive optical power, wherein a spacing between the first lens unit and the second lens unit is larger at a telephoto end than at a wide-angle end, a spacing between the second lens unit and the third lens unit is smaller at the telephoto end than at the wide-angle end, and a spacing between the third lens unit and the fourth lens unit is larger at the telephoto end than at the wide-angle end, and the following condition is satisfied: where D 3 a represents a distance on an optical axis from a surface closest to an object to a surface closest to an image in the first lens sub-unit, D 3 b represents a distance on the optical axis from a surface closest to the object to a surface closest to the image in the second lens sub-unit, and d represents the spacing between the first lens sub-unit and the second lens sub-unit.