Patent ID: 6384910
Filing Date: 2002-05-07
Classification: G01J,G01N

Abstract:
An optical system for detecting anomalies of a sample, comprising:focusing optics directing and focusing at least one beam of radiation along a path onto a spot on a surface of the sample; a first detector; collection optics receiving scattered radiation from the sample surface and originating from the at least one beam and focusing the scattered radiation to said first detector for sensing anomalies; a second, position sensitive, detector detecting a specular reflection of said at least one beam in order to detect any change in height of the surface at the spot; and a device altering the path of the at least one beam in response to the detected change in height of the surface at the spot to reduce position error of the spot caused by change in height of the surface at the spot, wherein said device alters said path without substantially moving the focusing optics.