Patent ID: 7265816

Claim:
An illumination optical system for illuminating a target surface using light from a light source, said illumination optical system comprising: a waveplate unit that includes first and second waveplates, the first and second waveplates converting incident light into linearly polarized light in polarization directions that are different from each other; a diffractive optical element unit that includes first and second diffractive optical elements that form illumination intensity distributions that are different from each other on a surface that substantially has a Fourier transformation relationship with the target surface; and an optical unit concurrently illuminating a first diffractive optical element and a second diffractive optical element of the diffractive optical element unit, wherein the first diffractive optical element receives linearly polarized light converted by the first waveplate, and the second diffractive optical element receives linearly polarized light converted by the second waveplate.