Patent ID: 7256949
Filing Date: 2007-08-14
Classification: G02B

Abstract:
1. An optical system comprising: a plurality of lens elements having respective lens surfaces; wherein an optical member having transmittance of 5% or less with respect to ultraviolet light over a wavelength range from 340 nm to 390 nm includes a first interference film formed on one of said lens surfaces, the following conditional expressions being satisfied: where Φ denotes the effective diameter of the lens surface, R denotes the radius of curvature of the lens surface, and B denotes an angle of the principal ray passing through the lens surface relative to the optical axis at the lens surface in the air side; and wherein the optical system includes a negative lens group and a positive lens group adjacent to the negative lens group; the negative lens group includes three lens elements which are a first negative lens element, a second negative lens element, and a positive lens element; and the lens surface is an image side surface of the second negative lens element.