Patent ID: 7522279

Claim:
A method of analyzing substantially the exact same spot on a sample with multiple wavelengths of electromagnetic radiation, comprising: practicing steps a and b in either order, said steps a and b being: a) providing a selection from the group consisting of: ellipsometer; polarimeter; spectrophotometer; and reflectometer; which sequentially comprises a source of polychromatic electromagnetic radiation, a stage for supporting a sample and a detector; b) providing a lens system, comprising at least one lens which len system has been designed to allow change of position of said at least one lens with respect to a sample, and which at least one lens optionally provides focal lengths which are substantially exactly the same at least two specified wavelengths; said method further comprising: c) placing said at least one lens of said lens system provided in step b prior to a sample which is positioned on said stage for supporting a sample; d) causing polychromatic electromagnetic radiation from said source thereof to become focused onto said sample by said at least one lens positioned before said sample, and obtaining data at least one wavelength at which said electromagnetic radiation is focused onto said sample at a point thereupon; e) moving said at least one lens along the locus of the electromagnetic radiation to place it at a different distance from said sample and again causing said polychromatic electromagnetic radiation from said source thereof to become focused onto said sample by said lens positioned before said sample, and obtaining data at least one wavelength at which the focal length is such that the polychromatic electromagnetic radiation is focused onto said sample at substantially exactly the same point thereupon as in step d; f) utilizing only data obtained which correspond to said substantially same point on said sample in sample analysis.