Patent ID: 7567345

Claim:
A reflectometer, ellipsometer, polarimeter or the like system comprising: a) a source of a beam of electromagnetic radiation; b) an aperture with a hole therethrough; c) a focusing means; and d) a stage for supporting a sample; each of said aperture, focusing means and sample being oriented in identifiable planes; such that in use said source of a beam of electromagnetic radiation is caused to direct a beam of electromagnetic radiation to a sample along an oblique angle of incidence thereto, the locus of the beam being oriented substantially perpendicular to the plane of said focusing means such that said beam passes through said focusing means and impinges upon a sample placed on said stage for supporting a sample, at an oblique angle of incidence (β) with respect to a normal to a surface of said sample, and the locus of the electromagnetic beam forms an angle (α) with respect to a normal to the plane of said aperture; said aperture, focusing means and stage for supporting a sample being oriented with respect to one another such that a projected plane of the aperture, a projected plane of the sample surface and a projected plane of the focusing means intersect, and such that the following condition is substantially met: Tan(α)=( X−f )/ f Tan(β); where “X” is the distance from the aperture, at the point at which said beam passes therethrough, to a center of said focusing means, and “f” is the focal length of said focusing means.