Method and apparatus for inspecting a substrate

A method of inspecting and/or characterizing a substrate, comprising:

• obtaining a first dataset (DA1), wherein said first dataset includes data derived from an image collected by a first detector of a first region of said substrate;
• obtaining a second dataset (DB1), wherein said second dataset includes data derived from an image collected by a second detector of at least a portion of said first region of said substrate;
• obtaining a third dataset (DA2), wherein said third dataset includes data derived from an image collected by said first detector from a second region of said substrate, wherein said second region of said substrate is expected to be substantially identical to said first region;
• obtaining a fourth dataset (DB2), wherein said fourth dataset includes data derived from an image collected by said second detector of at least a portion of said second region of said substrate;
• and
• processing information derived from said first, second, third and fourth datasets to detect a defect in at least one of said first or second regions using a generalized equation of a form
• A=(P(BDA1+CDB1)M/(SDA1+TDB1)Q+(EDA2+FDB2) N/(UDA2+VDB2)R)k,
• where values of B, C, E, F, M, K, P, Q, R, S, T, U, V, and N represent constants and/or functions of other variables, wherein said information processing further includes calculating a first function representing comparison between said first and third datasets and calculating a second function representing comparison between said second and fourth data sets;
• and
• classifying the detected defect using output values of the first and second functions.