US Patent 7292398 Optical system and optical apparatus including optical system

At least one exemplary embodiment is directed to an optical system which includes at least one first refractive optical element, which includes a solid material satisfying the following conditional expression (1), and at least one second refractive optical element, which includes a solid material satisfying the following conditional expression (2):−1.33×10−3×υd+6.7×10−1<θgF   (1)−1.63×10−3×υd+6.2×10−1>θgF   (2)where υd and θgF indicate the Abbe number and the partial dispersion ratio, respectively.