Patent ID: 7349082
Filing Date: 2008-03-25
Classification: G01N,G03F

Abstract:
1. A particle detection system configured to detect a particle on a surface of an object, the system comprising: a first radiation source configured to generate a beam of radiation having a first wavelength, the beam of radiation being directed to the surface of the object; a radiation detector system configured to output a plurality of detector signals corresponding to an intensity of radiation incident on the detector system; and a detection circuit coupled to the radiation detector system and configured to determine from the plurality of detector signals whether a particle is present on the surface of the object, wherein the detection circuit is configured to compare the plurality of detector signals with a predetermined threshold level, and to use a result of the comparison to distinguish a radiation signal associated with a particle, if present on the surface of the object, from a radiation signal associated with a diffraction pattern generated by the object.