Patent ID: 7764444
Filing Date: 2010-07-27
Classification: G02B

Abstract:
1. A three-unit zoom lens system comprising in order from an object side thereof: a first lens unit having a negative refracting power; a second lens unit having a positive refracting power; a third lens unit having one of a positive refracting power and a negative refracting power; and an aperture stop which is disposed at an image plane side of the first lens unit, and at an object side of a lens surface nearest to the image, of the second lens unit, and which moves integrally with the second lens unit, wherein at the time of zooming from a wide angle end to a telephoto end, a distance between the first lens unit and the second lens unit is narrowed, and a distance between the second lens unit and the third lens unit changes, and the second lens unit moves toward the object side at the time of zooming from the wide angle end to the telephoto end, and the second lens unit comprises a positive lens made of plastic, which is disposed nearest to the object, and the three-unit zoom lens system satisfies the following conditional expressions where, f f D D the overall length is a length which is obtained by adding a back focus expressed in terms of an air conversion length, to an optical axial thickness from a surface of incidence of a lens nearest to the object up to a surface of emergence of a lens nearest to the image, of the three-unit zoom lens system.