Patent ID: 8064148

Claim:
A catadioptric objective for inspecting a substrate using scattered radiation, comprising: a first optical group configured to transform radiation of a first polarization into radiation of a second polarization, wherein the first optical group comprises adjacently disposed at least two optical elements and a reflective element to reduce chromatic aberrations due to a spectral range of the radiation; a second optical group comprising a positive power refractive element configured to increase a numerical aperture of the catadioptric objective and a negative power refractive element; and a beamsplitter configured to provide radiation of the first polarization to the first optical group and radiation of the second polarization to the second optical group, wherein the negative power refractive element and the positive power refractive element of the second optical group disposed in order from the beamsplitter to an object and the negative power refractive element configured to increase the working distance between the beamsplitter and the object.