Patent ID: 7436503
Filing Date: 2008-10-14
Classification: G01N,G02B

Abstract:
1. An apparatus for inspecting a specimen by detecting optical beams scattered from the specimen, comprising: a beam generator for providing and directing an incident beam towards a specimen; an array subtraction device arranged to split an output beam, scattered from the specimen in response to the incident beam, into at least two secondary beams, spatially shift the at least two secondary beams relative to each other, and then recombine the secondary beams, wherein the recombining of the secondary beams causes (i) a periodic component, corresponding to at least one periodic structure on the specimen, to be subtracted from the recombined output beam, (ii) a ringing response to be substantially reduced or eliminated from the recombined output beam, and (iii) any actual defect components to be prevented from being subtracted from the recombined output beam; and a detector for receiving the recombined output beam and generating an output image or signal based on the recombined output beam.