Patent ID: 6078434
Filing Date: 2000-06-20
Classification: G02B

Abstract:
A zoom lens system comprising from an object side;a first lens unit located at the end of the lens system on the object side and having a negative optical power, anda second lens unit located at an image side of the first lens unit with a variable air space therebetween,wherein the first and second lens units are movable along an optical axis for zooming operation, and a lens element in at least one of said first and second lens units has a diffractive type optical surface, and wherein said diffractive optical surface satisfies the following condition:0.02<.vertline..phi.d/.phi..vertline.<0.2where.phi.d=-2m R2R2 is a second degree phase coefficient.m is the diffraction degree,.phi.=.phi.r+.phi.d represents the optical power of the lens,.phi.r is the optical power of the lens element, and.phi.d is the optical power of the diffractive optical element.