Patent ID: 8724882

Claim:
A method comprising: dividing a surface of a sample object into pixels which are characterized by a parameter variation; defining blocks of the surface as respective groups of the pixels; irradiating the pixels in multiple scans over the surface and applying differently oriented, respective first polarization states to an incident radiation; receiving returning radiation from the pixels in response to each of the scans; analyzing at least part of the returning radiation of the scans and applying respective second polarization states to said returning radiation to generate processed returning radiation from the returning radiation; detecting the processed returning radiation; for each of the scans, (i) constructing respective block signatures of the blocks in response to the processed returning radiation from the group of pixels in each block; and (ii) determining a block signature variation using the respective block signatures of the blocks; and in response to a correlation between the block signature variation and the parameter variation, selecting one of the first polarization states and at least one of the second polarization states for use in subsequent examination of a test object such that the combination of the at least two polarization states provides an optimal sensitivity of the block signature variation.