1. A method for detecting defects on a wafer, comprising: generating output for a wafer by scanning the wafer with an inspection system in first and second passes using a first optical state of the inspection system; generating first image data for the wafer using the output generated in the first pass and second image data for the wafer using the output generated in the second pass; combining the first image data and the second image data corresponding to substantially the same locations on the wafer thereby creating additional image data for the wafer; and detecting defects on the wafer using the additional image data.