Patent ID: 6721106
Filing Date: 2004-04-13
Classification: G02B

Abstract:
An optical device comprising:a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and an image sensor for converting an optical image formed by the zoom lens system into an electrical signal, wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power; wherein the third lens unit has an aspherical surface at the image side thereof; and wherein the following conditional formulae are fulfilled: âˆ’0.6X|âˆ’|X0|)/[C0Â·(Nâ€²âˆ’N)Â·f3]<0 0.1Ymax&lE;Y&lE;0.7Ymax wherein X represents a surface shape of the aspherical surface; X0 represents a surface shape of a reference spherical surface of the aspherical surface; C0 represents a curvature of the reference spherical surface of the aspherical surface; N represents a refractive index for a d-line of the object-side medium of the aspherical surface; Nâ€² represents the refractive index for the d-line of the image-side medium of the aspherical surface; f3 represents a focal length of the third lens unit; Ymax represents a maximum effective optical path of an aspherical surface; and Y represents a height in a direction perpendicular to an optical axis.