Patent ID: 8345357
Filing Date: 2013-01-01
Classification: G02B

Abstract:
1. An optical system which is used in a wavelength range including a near ultraviolet light range having a wavelength longer than approximately 350 nm and a visible light range, comprising: at least two first positive lenses satisfying the following conditional expressions (1) to (3) disposed closer to a contraction side than an aperture stop; and at least one second positive lens satisfying the following conditional expressions (1), (4) and (5): where, Vd denotes an Abbe number at the d-line, P=(Ng−NF)/(NF−NC), Ng denotes a refractive index at the g-line, NF denotes a refractive index at the F-line, NC denotes a refractive index at the C-line, and dN/dT denotes a rate of change of the refractive index with respect to temperature in a vicinity of room temperature.