Patent ID: 7307795
Filing Date: 2007-12-11
Classification: G02B

Abstract:
1. A zoom lens comprising in succession from an object side to an image side: a first lens unit of negative optical power including a negative lens element and a positive lens element, the object side and image side surfaces of the negative lens element of the first lens unit are aspherical surfaces; a second lens unit of positive optical power; and a third lens unit of positive optical power; wherein an interval between adjacent ones of the lens units changes in case of zooming, wherein said negative lens element of said first lens unit is of a meniscus shape convex toward the object side, and the image side surface of said negative lens element of said first lens unit is of an aspherical shape in which the negative optical power weakens from away an optical axis, and when at a maximum height whereat an off-axial ray passes through said negative lens element at a wide angle end, a difference between a sag amount from a paraxial radius of curvature of the object side surface of said negative lens element and the sag amount of said aspherical shape is defined as Sag where the signs of Sag 1 and Sag 2 are minus when the surface shape of the paraxial radius of curvature is more adjacent to the object side than the aspherical shape, and are plus in a case converse thereto.