Patent ID: 7184138

Claim:
A sample inspection system, comprising: collection optics that receive radiation scattered from a point on a sample surface proximate a symmetry axis of said collection optics and originating from an incident radiation directed at an oblique angle with respect to said sample surface, said collection optics being further configured to direct the scattered radiation to a detector a spatial filter disposed between said collection optics and the detector, said spatial filter being configured to screen the detector from substantially all of the scattered radiation that is scattered in a direction having a forward azimuthal component relative to the incident radiation, said spatial filter or system being configured to screen the detector from the scattered radiation scattered in a direction having a backward azimuthal component relative to the incident radiation and an elevation angle less than about 45° with respect to a normal to the surface whereby the detector is screened from forward scattered noise while a backscattered signal is allowed to reach the detector.