Patent attributes
A zoom lens includes, from the object side, first and second lens units of negative and positive refractive power. The lens units move during zooming from the wide-angle end to the telephoto end. The first lens unit includes, from the object side, three negative lenses and a positive lens, at least one of the surfaces of these lenses being aspherical. A spherical surface whose center of curvature is on the optical axis and that includes a point of the intersection of a lens surface and the optical axis and a point on the lens surface determined by the effective aperture is referred to as reference spherical surface of the lens surface. In the first lens unit, the radiuses of curvature of the image-side reference spherical surface of the most object-side negative lens and the object-side reference spherical surface of the second most object-side negative lens are appropriately set.
