Patent ID: 6456443
Filing Date: 2002-09-24
Classification: G02B

Abstract:
A zoom lens apparatus comprising:a zoom lens system forming an optical image of an object; and an image sensor for receiving the optical image formed by said zoom lens system, wherein said zoom lens system includes, in order from the object side thereof; a first lens unit having a negative power; a second lens unite including at least one positive lens element and one negative lens element and having a positive power; and a third lens unit having a positive power, wherein zooming is achieved by moving at least two lens units in such a way that a distance between said first and second lens units and a distance between said second and third lens units vary, and wherein at least one lens element included in said lens units is a plastic lens element, and fulfills the following conditions: âˆ’0.8Ã—(Nâ€²âˆ’N)&phgr;W<0.8 âˆ’0.453/M2<0.90 (where &phgr;T/&phgr;W>1.6) whereCp represents a curvature of said at least one plastic lens element; &phgr;W represents a power of the entire zoom lens system at a wide-angle end; N represents a refractive index for a d-line of a medium existing on an object side of an aspherical surface; Nâ€² represents a refractive index for a d-line of a medium existing on an image side of the aspherical surface; M3 represents an amount of movement of said third lens unit (a negative value representing a movement toward the object side with respect to a position of said third lens unit at the wide-angle end); M2 represents an amount of movement of said second lens unit (a negative value representing a movement toward the object side with respect to a position of said second lens unit at the wide-angle end); and &phgr;T represents a power of the entire zoom lens system at a telephoto end.